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The thought is in the question; the information is in the answer. 

AUDELS 

ANSWERS 

ON 

PRACTICAL 
ENGINEERING 

FOR 

ENGINEERS, FIREMEN, 
MACHINISTS, 

AND THOSE DESIRING TO ACQUIRE A WORKING 

KNOWLEDGE OF THE THEORY AND 

PRACTICE OF STEAM ENGINEERING 

A PRACTICAL TREATISE 

with ILUSTRATIONS 
By GIDEON HARRIS and Associates 



^ 



THEO. AUDEL & CO., Publishers 

72 Fifth Avenue, New York 



T i * 7 1 



COPYRIGHTED, 1912, 

BY 

THEO. AUDEL & CO., 
New York. 



\ 



J-' 



\* 




Printed in the United States. 

gCI.A312560 



PREFACE 



This book is written for the special information of 
engineers, machinists, firemen and electricians who must, 
sooner or later, procure an engineers' license by going 
before a board of practical engineers and answering 
questions relating to the care of boilers, pumps, injectors, 
engines, indicator, safety valve and the dynamo, etc. 

The author in the preparation of the work has had 
two objects constantly in view; first to cause the student 
to become familiarly acquainted with the leading prin- 
ciples of his profession as they are mentioned, and sec- 
ondly, to furnish him with as much advice and informa- 
tion as possible within the reasonable limits of the 
work. 

The question and answer form of presenting informa- 
tion appeals strongly to the practical man who wants a 
simple answer to a plain question without a display of 
technical terms or higher mathematics. 

When technical terms are used they are either explained 
or made clear by the wording of the answer. In order not 



PREFACE 

to divert the mind and confuse the reader, the answer is 
always made short and direct, giving simply the informa- 
tion demanded by the question. 

Detailed explanations, or items of seeondary importance, are 
printed in small type in separate paragraphs. 

This is not a book of theories — it is practical, the aim 
of the author being to present the different subjects treated 
in as simple a form as possible so anyone can understand 
it. 

With this in view, the author has been careful to omit 
all unnecessary mathematics, and to present only such 
information as will be needed to prepare the reader for 
all emergencies, and for questions of the examining 
inspector or prospective employer. 

THE AUTHOR. 




TABLE OF CONTENTS 



Pages 
AIR 1 to 2 

Its composition — weight — volume — expansion 
— quantity required for combustion. 

WATER 3 to 7 

Properties of water — boiling point — weight of 
ice — compression of water — nitration — latent 
heat of fusion — latent heat of water — evapora- 
tion. 

STEAM 8 to 11 

Kinds of steam — properties — latent heat of 
steam — usual working pressures — superheated 
steam. 

FUEL AND HEAT 12 to 20 

Classes of fuel — evaporation per pound of coal — 
coal per horse power — coal per sq. ft. of grate — 
firing with hard and soft coal — cleaning the 
fire — banking — carbon — cu. ft. of coal per ton — 
draught — mechanical equivalent of heat — ther- 
mometer scales — absolute zero. 

STEAM BOILERS 21 to 23 

Classification of boilers — comparison of types — 
steam domes. 



TABLE OF CONTENTS 



BOILER CONSTRUCTION .... 24 to 45 

Materials — tensile strength — elongation — elas- 
tic limit — flange steel — tube sheets — tubes and 

pipes rivetted joints — shearing strength of 

rivets — details of riveting — calking — rules for 
calculating stresses in boilers — domes — dry pipe 
— braces — allowable stress on stays — manholes 
— factor of safety — bursting pressure — safe 
working pressure — hammer test — hydraulic test 
— boiler horse power — standard dimensions of 
boilers — grate and heating surface — evapora- 
tion — amount of coal burned — heat losses. 

WATER TUBE BOILERS 46 to 50 

Advantages — disadvantages — description of sta- 
tionary and marine types — ■ circulation. 

THE STEAM GAUGE 51 to 54 

Principle of the steam gauge — the two types of 
gauge — test — precautions — gauge pressure. 

THE SAFETY VALVE 55 to 70 

Its function — precaution — rules for size — types 
— method of attaching — ad j ustment — ' ' pop ' ' 
valves — kind of gauge to use with outside spring 
— safety valve rules — simple explanation of the 
principle of the safety valve formula — problems 

PROPERTIES OF SATURATED 
STEAM 71 

Pressure : — temperature — latent heat — density 
volume — weight. 

INSTALLATION OF BOILERS ... 72 to 79 

Method of setting a horizontal boiler — provision 
for expansion — dead plate — a modern suspen- 
sion boiler setting — arch plate — grate bars — 
mud drum — surface blow off — blow off pipe — 
feed pipe — fusible plug — main stop valve — 
check valve — damper — chimneys 



TABLE OF CONTENTS 



MANAGEMENT OF BOILERS ... 80 to 92 

Duties of engineer and fireman — filling the 
boiler — priming — cracked fronts — cleaning the 
tubes — tube repairs — fusible plugs — plate trou- 
bles — scale — the feed water — analysis of average 
boiler scale — kerosene — boiler tests — prepara- 
tion for a test — the inspection — exposed parts of 
boiler. 

ENGINEERS' LAW . 93 to 97 

Requirements for candidates for engineer's 
license — rules for operating. 

FIREMEN'S LAW . 98 to 100 

Requirements for license and rules governing the 
operation of boilers. 

STEAM ENGINES 101 to 106 

Classes of engine — slide valve engine — "auto- 
matic" engine — Corliss engine — economy of 
different types — regulation of speed — materials 
— parts — stresses on parts — bearings. 

THE VALVE AND VALVE GEAR . . 107 to 114 

Description of the slide valve — limitations of the 
slide valve — lap — cut off — lead — angular ad- 
vance — travel — clearance — valve setting. 

THE CORLISS ENGINE 115 to 124 

Advantages — lap clearance — compression — di- 
rections for setting Corliss valves — method of 
adjusting the cut off — dash pots. 

ARITHMETIC OF THE STEAM 
ENGINE 125 to 132 

Calculating the piston speed — usual piston 
speeds — stroke — area of piston — mean effective 
pressure (M. E. P.) — horse power — indicator 
cards — the indicator. 



TABLE OF CONTENTS 



LUBRICATORS 133 to 142 

Feeds for external lubrication — sight feed lubri- 
cator — principle of operation of a sight feed 
lubricator — construction of sight feed lubricator 
— method of attaching to steam pipe — refilling 
— regulation of feed — sight feed oil cups — 
graphite and grease cups — points relating to 
sight feed lubricators. 

INSTALLATION AND OPERATION 
OF ENGINES 143 to 150 

Foundations — alignment — j oints — lubrication 
and friction — points relating to lubricants — how 
to lay up an engine — gaskets — packings — throt- 
tling governors — rebabbitting a bearing — speed 
indicator — condensers. 

STEAM PUMPS 151 to 164 

Hydraulics — practical lift — pressure — pumping 
hot water — cylinder proportions — simple pumps 
— compound pumps — elevator pumps — the valve 
gear — fire pumps — centrifugal pumps — economy 
of compound pump — directions for setting the 
valves of duplex pumps — pump troubles — water 
valves — pistons and plungers — method of piping 
a pump — air chambers — pump calculations: 
size, horse power, etc. 

INJECTORS 165 to 169 

Principle of the injector— -single and double tube 
injectors — operation with hot water — method of 
piping an injector — injector troubles — operation 
on low and high pressures. 

FEED WATER HEATERS .... 170 to 172 

Classes of feed water heater — open and closed 
heaters — pipe connections — economy due to 
heating the feed water. 



TABLE OF CONTENTS 



STEAM HEATING 173 to 180 

The one pipe system — the two pipe system — 
operation — choice of systems — gravity system — 
air in radiators — automatic air valves — pressure 
for heating — capacity of radiators — exhaust 
steam heating — pipe connections — pump gover- 



STEAM TRAPS 181 to 184 

Classes of steam trap — return trap — operation — 
separators — location of trap. 

BELTS, GEARS, AND PULLEYS . 185 to 188 

Method of operating belts — quarter turn belt — ■ 
open and cross belts — belt calculations — horse 
power transmitted by belts. 

STEAM TURBINES 189 to 196 

Classes of turbine — description of Parsons- 
Westinghouse turbine — governors — reason for 
high vacuum — working pressures — the De 
Laval turbine — the Curtis turbine. 

OUTLINE OF REFRIGERATION . . 197 to 204 

Definition — how low temperature is obtained — 
mechanical refrigeration — choice of heat me- 
dium — substances used in refrigeration — advan- 
tages of ammonia — the compression system — 
the absorption system — dry and wet compres- 



PRACTICAL ELECTRICITY ... 205 to 242 

Electricity — magnetism — induction — volt-ohm 
— ampere — Ohm's law — watt — electrical horse 
power — capacity of wires — drop — the dynamo — 
classes of dynamo: series, shunt and compound 
— choice of types — overcompounding — care of 
dynamo — sparking — switchboard connections — 



TABLE OF CONTENTS 



PRACTICAL ELECTRICITY— Continued. 

wiring — circuit breakers — windings — starting 
box — motors — primary cells — secondary cells — 
charging — sulphation — electrolyte — Edison 
three wire system — dynamotor — fuses — the 
alternating current — advantages of alternat- 
ing current — transformers — rotary convert- 
ers — alternators — classes of alternator — poly- 
phase distribution — comparison of different 
systems of distribution — alternating current 
motors — recording watt hour meter — power 
factor — kilovolt ampere 

ELEVATORS 243 to 254 

Different types — control and safety devices — 
electric elevators — hydraulic elevators — safety 
governor — control of water valve — pilot valve — 
horizontal hydraulic elevators — plunger eleva- 
tors — working pressures 



PRACTICAL ENGINEERING 



AIR 



Ones. What is air? 

Ans. Air is a mechanical mixture of two gases, 
nitrogen and oxygen, with traces of carbonic acid 
gas. The relative volumes are: Nitrogen, 4 parts; 
oxygen, 1 part. 

Ques. Does air have weight? 

Ans. Yes; all the air surrounding the earth has 
sufficient weight to cause a pressure of 14.7 pounds 
per square inch at sea level. 

Ques. What is the volume of a pound of air? 

Ans. At a temperature of 62 degrees F. at sea 
level, 13.14 cubic feet weigh one pound. 

Ques. What efEect has heat on air? 

Ans. Like almost all other gases, fluids and solids, 
air expands as heat is applied. 

Ques. Is the expansion of a gas proportional 
to the amount of heat applied ? 

Ans. Yes; the volume of a perfect gas increases 
273- of its volume at Centigrade for every increase 
of temperature of 1 C. 



AUDELS ANSWERS ON 



Ques. What may be said of oxygen, one of 
the gases that compose air? 

Ans. Oxygen is often spoken of as the supporter 
of combustion, and animal life. 

Ones. What is a vacuum? 

Ans. A space devoid of all matter. 

Ques. What is the object of an air pump 
on a condenser? 

Ans. To abstract the water condensed, and the 
air which was originally contained in the water when 
it entered the boiler. 



PRACTICAL ENGINEERING 



WATER 



Ques. What is water? 

Ans. Water is a chemical composition of two 
gases: oxygen and hydrogen. 

Ques. What do the characters H 2 signify 
when written after the word " water"? 

Ans. They mean that water is composed of two 
atoms hydrogen to one atom oxygen. 

Ques. What is the pressure at the base of a 
column of pure water, at a temperature of 
62° F., one foot high? 

Ans. .434 of a pound per square inch. 

Ques. What are the relative weights of water 
and mercury? 

Ans. Water is about 13.6 times lighter than mer- 
cury. 

Ques. What proof have we that this is the 
case? 

Ans. At the sea level the pressure of the atmos- 
phere (14.7 pounds) will balance a column of water 



AUDELS ANSWERS ON 



34 feet high; this same pressure will balance a col- 
umn of mercury only 30 inches high, so the formula 

34 X 12 

= 13.6 must give the number of times mercury 

is heavier than water. 

Ques. At what temperature is water at its 
maximum density? 

Ans. At 39 degrees Fahrenheit. 

Ques. What is the most remarkable charac- 
teristic of water? 

Ans. Water at its maximum density (39.1 degrees 
F.) will expand as heat is added, and it will also expand 
slightly as the temperature falls from this point. 

Ques. How much will pure water expand? 

Ans. As the temperature of water is raised from 
39.1° F. (point of maximum density) to 212° F. 
(boiling point) it will expand 4jq per cent. 

Ques. What is the weight of one gallon of 
pure water? 

Ans. One gallon of pure water (U. S. standard 
gallon) will weight about 8J^ pounds and contains 
231 cubic inches. 

The weight here given is correct when the water is at a tem- 
perature of 65° F. 



PRACTICAL ENGINEERING 



Ques. At what temperature does water freeze 
and boil? 

Ans. Water at atmospheric pressure at the sea 
level will freeze at 32 degrees F. and will boil at 212 
degrees F. 

Ques. Is the boiling point of water the same 
in all places? 

Ans. No; the boiling point of water will lower as 
the altitude increases; at an altitude of 5,000 feet 
water will boil at a temperature of 202 degrees F. 

Ones. How does pressure affect the boiling 
point of water? 

Ans. An increase of pressure will elevate the boiling 
point. 

Ques. What is the weight of a cubic foot of 
water? 

Ans. It varies with the temperature ; at the freez- 
ing point, 32° F., 1 cu. ft. of water weighs 62.42 lbs., 
and at the boiling point, 212° F., it weighs 59.76 lbs. 
For ordinary calculations it is taken at 62.4 or roughly 
62 lbs. 

Ques. Is a cubic foot of ice lighter or heavier 
than a cubic foot of water? 

Ans. A cubic foot of ice at 32° F. weighs 57.5 lbs. ; 
the relative volume of ice to water at 32° F. is 1.0855, 
the expansion in passing into the solid state being 8.55 
per cent. Specific gravity of ice = .922. 



AUDELS ANSWERS ON 



Ones. Can water be compressed? 

Ans. Yes, but very little indeed; it is said that 
under a pressure of 130,000 pounds per square inch 
16 volumes may be compressed to occupy the space of 
15 volumes, under atmospheric pressure. 

Ques. What is meant by pure water ? 

Ans. Water free from impurities held either in 
suspension or solution. 

Ones. Is absolutely pure water ever found? 

Ans. Pure water, strictly speaking, is rarely if 
ever found. The principal impurities are salt, lime, 
magnesia, etc. One thousand gallons of ordinary 
fresh water will contain about twelve pounds of solid 
matter. 

Ones. Can water be purified wholly by filtra- 
tion? 

Ans. Water can only be partially purified by 
filtration, as none of the impurities of water con- 
tained in solution will separate until about 325 degrees 
of heat are applied. 

Ques. What is meant by the latent heat of 
fusion of ice? 

Ans. The amount of heat necessary to convert a 
pound of ice into water at the same temperature. 

Ones. What is the latent heat of fusion of 
ice? 

Ans. 143 heat units; that is, it takes 143 heat 



PRACTICAL ENGINEERING 



units to convert one pound of pure ice into water at 
the same temperature. 

Ques. Is there any substance known that 
has a greater latent heat than water? 

Ans. No. 

Ques. What is a heat unit? 

Ans. The amount of heat necessary to raise the 
temperature of one pound of water one degree F. 

Ques. What other qualities does water con- 
tain? 

Ans. Water contains the greatest absorbing qual- 
ities of any known substance. 

Ques. At what temperature does water evap- 
orate? 

Ans. At any temperature above 32 degrees F. 



AUDELS ANSWERS ON 



STEAM 



Ques. What is steam? 

Ans. The vapor of water; the hot invisible vapor 
given off by water at its boiling point, the latter 
depending upon the pressure. 

The visible white vapor popularly known as steam is not 
steam, but a collection of fine watery particles, formed by the 
condensation of steam. 

Ones. Define the different kinds of steam? 

Ans. Steam is said to be: 1, — saturated when its 
temperature corresponds to its pressure; 2, — super- 
heated when its temperature is above that due to its 
pressure; 3, — gaseous steam or steam gas when it is 
highly superheated; 4, — dry when it contains no moist- 
ure. It may be either saturated or superheated; 
5, — wet when it contains intermingled mist or spray, 
its temperature corresponding to its pressure. 

Ques. Has steam weight, and if so, is it 
lighter or heavier than air? 

Ans. Yes; steam has weight and it is about one- 
half the weight of air at atmospheric pressure; one 
pound of steam at atmospheric pressure will have a 
volume of 26.79 cubic feet. 



PRACTICAL ENGINEERING 9 

Ques. What will be the volume of a pound 
of steam at 100 pounds gauge pressure? 

Ans. 3.91 cubic feet. 

Ques. In what way does the pressure affect 
the temperature of steam? 

Ans. The temperature of steam will rise as the 
pressure increases ; at atmospheric pressure steam will 
have a temperature of 212 degrees F. At 50 pounds 
pressure above vacuum a temperature of 281 degrees 
F., and at 100 pounds pressure above vacuum the 
temperature will be 327.8 degrees. 

Ques. If you were required to find the tem- 
perature of steam corresponding to a certain 
pressure, how would you find it? 

Ans. By referring to the steam table, given on 
page 71. 

Ones. What is meant by the latent heat of 
steam? 

Ans. It is the amount of heat required to change 
one pound of water into steam of the same tempera- 
ture. 

The latent heat varies with the boiling point, that is, it de- 
creases as the pressure rises. 

Ques. Explain more fully the meaning of 
latent heat of steam. 

Ans. If heat be applied to a pound of pure water 
having a temperature of 212 degrees F., steam will 
be formed and in a short time all the water will be 



10 AUDELS ANSWERS ON 

evaporated; now if the temperature of the steam so 
formed be taken, the thermometer will register the 
same as the boiling water, 212 degrees. It has been 
accurately determined by experiment that 970.4 
degrees of heat, or heat units, must be applied to a 
pound of boiling water to change it into steam of the 
same temperature, and this heat is called the latent 
heat of steam. 

Ques. What is the relative volume of steam 
and water at atmospheric pressure? 

Ans. Water evaporated into steam will increase 
in volume or bulk 1646 times. 

Ques. What are the usual working pressures 
employed for different purposes? 

Ans. For steam heating from one to ten pounds. 
For power purposes from 20 to 200 pounds. In large 
mills and factories from 80 to 200 pounds; on loco- 
motives from 150 to 225 pounds; on board ocean 
liners and war ships from 150 to 300 pounds. 

Ques. What is the object of superheating 
steam? 

Ans. To raise the temperature of the steam, with- 
out perceptibly raising the pressure; the excess heat 
is desirable in order to diminish or prevent condensa- 
tion in an engine cylinder. 

Ques. Does superheated steam follow the 
laws of saturated steam? 

Ans. No. 



PRACTICAL ENGINEERING 11 

Ques. Is superheated steam extensively used ? 

Ans. Yes; it is used extensively in power plants 
and much attention is being given to the design of 
engines for superheated steam, as the economy by 
its use is an established fact. 

The saving in feed water due to superheating the steam is a 
little over 1 per cent, for each 10° of superheat. 

Ques. Name a common type of boiler in 
which the steam is slightly superheated. 

Ans. In the vertical or upright boiler the steam 
is slightly superheated by reason of its being in con- 
tact with the upper part of boiler tubes, which are 
above the water line. 



12 AUDELS ANSWERS ON 



FUEL AND HEAT 



Ques. What fuels are used for making steam ? 

Ans. Anthracite coal (hard), bituminous coal 
(soft), wood, petroleum and other liquid fuels. 

Ques. Of what value is wood compared to 
coal for steam making? 

Ans. One ton of good average coal is equal to 
about 13^2 cords (192 cubic feet) of wood. 

Ques. How much water can be evaporated 
by one pound of the best coal> 

Ans. Under favorable conditions we can evap- 
orate about 11 pounds of water with one pound of 
good coal; this high average is only realized in very 
efficient modern plants. The general average will be 
about from 7 to 9 pounds of water evaporated per 
pound of coal, on account of lack of attention on the 
part of those in charge of the boiler or badly propor- 
tioned boiler. 

Ques. Is all the heat extracted from the coal 
while on the grate? 

Ans. No; the gaseous part of the coal burns in 
the space above and back of the grate. 



PRACTICAL ENGINEERING 



13 



Ques. How much coal is used per horse- 
power per hour in ordinary plants? 

Ans. About 3 to 4 pounds of coal per hour for 
every horse power developed. 

Ques. How much coal is used per horse 
power in large modern power houses? 

Ans. Large power houses having modern triple 
expansion engines use as little as 1J^ pounds of coal 
per hour for every horse power developed. 




X///////A 



Fig. 2. — Firing with even depth of fuel on the grate, resulting in a uniform gen- 
eration of gas throughout the charge. 

Ques. How much coal may be burned per 
square foot of grate surface? 

Ans. About 14 pounds is as much as can be burned 
per square foot of grate surface, although this may be 
greatly increased by forced draught. 

Ques. Describe how you would fire with hard 
coal? 

Ans. When firing with hard coal, the fire should 



14 AUDELS ANSWERS ON 

be carried as level as possible, and just thick enough 
to allow the draught to pass through the fire freely. 
A hard coal fire must not be raked or poked on top. 
If necessary to slice the fire, a bar should be run 
under the bed of fire next to the grates and the lower 
ashes worked through the grate openings. 

Ques. How thick would you carry a hard 
coal fire? 

Ans. This depends altogether on the draught. 
With a poor draught a thin fire must be carried ; with 
a strong draught, the fire bed may be quite thick; 
but no hard coal fire should be allowed to get thicker 
than nine inches. 

Ques. How would you fire with soft coal? 

Ans. When firing with soft coal the fire should 
be carried as level as possible and as thick as the 
draught will allow. In order to get the best results 
out of a soft coal fire, it requires frequent breaking 
up. This is done by running a bar in fire next to 
grates and lifting it up and breaking up the large 
lumps; soft coal is most inclined to cake up when 
wet, and for this reason it should be used dry if 
possible. 

Ques. How would you clean a fire? 

Ans. When a fire becomes so thick that the 
draught does not readily go through, it must be 
cleaned, and this is best done by pushing the top 
of good fire back to the bridge wall; the clinkers and 



PRACTICAL ENGINEERING, 15 

ashes may now be hauled out and the good fire pulled 
forward; after which the ashes from back part of 
grate may be pulled over the fire and out of furnace 
doors. The remaining fire is now spread evenly over 
the entire grate, carefully leveled and covered thinly 
with coal. 

Ques. How would you clean a fire if the 
boiler were fitted with dumping grates? 

Ans. By pushing all the good fire back on the 
second section ; the first section may now be dumped 
in ash pit, and fire pulled forward and the second 
section dumped. The fire is now evenly spread as 
before and covered with coal. 

Ques. How would you bank a fire? 

Ans. By shoving the fire back to bridge wall and 
covering thickly with coal, leaving about one-half the 
grate surface exposed. 

Ques. How much carbon does hard coal 
contain ? 

Ans. From 80 to 90 per cent. 

Ques. How much carbon does soft coal con- 
tain? 

Ans. Only from 45 to 72 per cent. 

Ones. What do you understand by carbon? 

Ans. Carbon is the solid part of coal which burns 
on the grate. 



16 ^ AUDELS ANSWERS ON 

Ques. How many heat units does one pound 
of average coal contain? 

Ans. From 10,000 to 15,000 heat units. 

Ques. What other substances are contained 
in coal? 

Ans. Coal tar, sulphur, iron and slate; usually 
these only form a small percentage. 

Ques. How many cubic feet will a ton of hard 
coal contain? 

Ans. Per ton of 2,240 lbs., it varies according to 
quality and size from 36 to 41 cu. ft. 

Ques. What causes draught? 

Ans. Draught is caused and maintained by the 
difference in weight of the hot gases in the stack and 
the cold air surrounding the stack. 

Ones. Describe more fully the theory of 
draught? 

Ans. The air inside of a chimney will always be 
somewhat hotter than the outer air, and it will 
expand and rise to the top and flow out of the chim- 
ney. Now as this air flows out, other air must take 
its place, and in a boiler furnace this air can only 
come from under the grates, and it must pass through 
the fire under the boiler and through the tubes into 
the smoke connection. This circulation of air is 
maintained constant as long as there is a differ- 
ence of temperature in and outside the chimney; the 



PRACTICAL ENGINEERING 



17 



greater the difference of temperature, other condi- 
tions remaining the same, the stronger will be the 
draught. 

Ones. Is it possible to build and maintain a 
fire without air? 

Ans. No. A large amount of air is necessary in 
order to maintain a fire. About 14 pounds of air are 
required for every pound of coal burned. 




Fig. 3. — Illustrating the usual method of obtaining forced draught on steam- 
boats. The boilers are placed in an air tight, room and air under pressure 
is supplied by a centrifugal fan. In somi cases- the ash pan of the boiler is 
made air tight and connected direct to the outlet of the fan. 



Ques. What is the mechanical equivalent of 
heat? 

Ans. The amount of heat necessary to raise the 
temperature of a pound of water one degree F. is 
equivalent to the mechanical power that will raise a 
weight of 778 pounds one foot. 



18 



AUDELS ANSWERS ON 



Ques. How are the temperatures of different 
substances ascertained ? 

Ans. By the thermometer. There are three ther- 
mometers in general use, but as the Fahrenheit ther- 




Pig. 4. — The mechanical equivalent of heat. In 1843, Dr. Joule of Manchester, 
England, performed his classic experiment, which revealed to the world the 
mechanical equivalent of heat. As shown in the figure, a paddle was made 
to revolve with as little friction as possible in a vessel containing a pound of 
water whose temperature was known. The paddle was actuated by a known 
weight falling through a known distance. A pound falling through a distance 
of one foot gives a foot pound of energy. At the beginning of the experiment 
a thermometer was placed in the water, and the temperature noted. The 
paddle was made to revolve by the falling weight. When 772 foot pounds 
of energy had been expended on the pound of water, the temperature of the 
latter had risen one degree, and the relationship between heat and mechan- 
ical work was found. Later determinations made with more refined appa- 
ratus have shown that the correct figure is 778 foot pounds. 

mometer is the standard in this country, this instru- 
ment only will be described. The Fahrenheit ther- 
mometer consists of a glass tube having a very small 
bore ; the lower end of which opens into a bulb or small 
reservoir, the upper end of the tube is sealed after all 



PRACTICAL ENGINEERING 



19 



the air has been exhausted. The bulb of this instru- 
ment is filled with mercury, such a quantity being 
used that when the bulb of the instrument is immersed 
in boiling water the expanding mercury will be forced 
to a point near the top of the tube. This point is 
marked 212 degrees and is the boiling point of water. 




n FREEZING POINT 

OF WATER 



Fig. 5. — Comparison of thermometer scales. The figure shows the freezing 
and boiling points respectively of the Centigrade, Fahrenheit and Reaumur 
thermometer scales. 



The bulb of the instrument is now plunged into 
cracked ice and the contracting mercury will rapidly 
fall in the tube; when it gets as low as it will go, that 
point is marked 32 degrees, and is the freezing point 
of water. The space between the boiling and freezing 
points is graduated into 180 parts or degrees. The 
space under the freezing point is graduated to 0, which 



20 



AUDELS ANSWERS ON 



is called zero in this instrument, the scale being con- 
tinued as far as necessary below zero. 

Ones. What is the meaning of absolute zero? 

Ans. Absolute zero is the point where all heat 
action ends and is said to be 459.2 degrees below the 
zero on the Fahrenheit thermometer. 

Ques. Give the relative heating values of some 
of the various fuels. 

Ans. They are as follows: 

1 lb. turf and peat will raise 28 lbs. of water from 32° to 212° F. 



undried wood " 


" 27 


dried «* " 


" 36 


soft coal 


" 60 


alcohol 


" 67| 


charcoal 


" 75 



PRACTICAL ENGINEERING 21 



STEAM BOILERS 



Ques. What is a steam boiler? 

Ans. A steam boiler is a very strongly built vessel 
in which steam is generated. 

Ques. What are the chief functions of a 
steam boiler? 

Ans. To hold the water we wish to turn into 
steam and to transfer the heat to the water. 

Ques. Name some types of boiler in common 
use. 

Ans. The horizontal return tubular, the water 
tube, the vertical or upright, locomotive boilers and 
marine boilers. 

Ques. Give some of the good features of the 
horizontal return tubular boiler, also a brief 
description. 

Ans. The horizontal tubular boiler consists of a 
cylindrical shell having a head or tube sheet riveted 
into each end. These tube sheets or heads are 



22 AUDELS ANSWERS ON 

provided with numerous holes into which tubes are 
expanded, to provide more heating surface and also 
to prevent the head bulging out from the effect of 
the pressure. In this type of boiler the only parts 
requiring to be braced is a small segment above the 
tubes, and also below the tubes if the boiler be more 
than 72 inches in diameter. The good features of this 
boiler are that it is cheap at first cost, requires few 
repairs, and as all parts are fairly accessible, repairs 
may be easily made when necessary. This type of 
boiler has ample water and steam space and is there- 
fore not liable to prime. 

Ques. What are the bad features of this 
boiler? 

Ans. Internal strains due to unequal expansion. 
When the boiler is started the shell plates, back head 
and tubes will become hot rapidly, while the upper 
parts of boiler will remain cold until steam begins 
to form ; this causes unequal expansion, which causes 
severe strains ; in fact greater strains than that due 
to regular service. It is not to be recommended for 
high pressures, especially in the larger sizes, on 
account of the thick plates and riveted joints ex- 
posed to the intense heat of the furnace. 

Ques. What else may be said against this 
boiler? 

Ans. This boiler is set up and supported by brick- 
work which must be kept in repair. If the brickwork 



PRACTICAL ENGINEERING 23 



in furnace be neglected the whole boiler might settle 
and break off the main steam pipe. Also this boiler, 
being built in one piece, the larger sizes are very 
heavy and hard to transport; another objection to 
this type of boiler is that its diameter is restricted 
because of the objection to thick shell plates exposed 
to the intense heat of the furnace. 




Fig. 6.— Horizontal return tubular boiler and setting; this type of boiler is 
suitable for low and moderate steam pressures. 

Ques. What may be said of steam domes on 
boilers of this type? 

Ans. Steam domes are supposed to furnish dry 
steam, but most boilers of this type are now built 
without domes. 

In the absence of a dome, a dry pipe (see fig. 9) should be 
provided, because the ordinary horizontal boiler delivers steam 
containing about 2 per cent, of moisture. 



24 AUDELS ANSWERS ON 

BOILER 
CONSTRUCTION 



Ones. What materials are used in the con- 
struction of horizontal tubular boilers? 

Ans. The shell, heads, tubes and rivets are made 
of steel; all stays and braces of best double refined 
iron; the front, nozzles and other fixtures are usually 
made of cast iron. 

Ques. How is this boiler held in position? 

Ans. Heavy cast iron lugs are riveted to the sides 
of boiler so that the bottom of lug will be about 3 
inches above the center of boiler ; these lugs should be 
about 10 inches wide and project about 12 inches into 
the walls of the setting. With an iron plate 1 inch 
thick under the lug the bottom of brick under plate 
will form the fire line, which should be just at the 
extreme diameter or center of boiler. 

Ques. How many lugs should a boiler have? 

Ans. Small boilers usually have four lugs, two on 
each side; boilers over 60 inches in diameter should 
have three or four lugs on each side. 



PRACTICAL ENGINEERING 25 

Ques. Define the term tensile strength? 

Ans. Tensile strength is the amount of force 
(pulling) which when slowly and steadily applied 
to a bar or plate of iron or steel will pull it apart. 
Tensile strength is always expressed in pounds per 
square inch, hence, the statement that a boiler plate 
has a tensile strength of 60,000 pounds per square 



Fig. 7. — Cross section of a horizontal return tubular boiler showing circulation 
of the water. 

inch, means that a section of the plate having an 
area of one square inch will break under a pull of 
60,000 pounds. 

Ones. What should be the tensile strength 
of good boiler plate? 

Ans. From 55,000 to 60,000 pounds per square 
inch. 



26 AUDELS ANSWERS ON 

Ques. Can steel be made with a higher 
tensile strength than 60,000 pounds? 

Ans. Yes ; steel may be procured having a tensile 
strength of 100,000 pounds per square inch or more, 
but this steel cannot be flanged; it is hard and 
has other qualities which make it undesirable to use 
as boiler plate. 

Ques. What should be the tensile strength 
of rivets used in boiler construction? 

Ans. From 55,000 to 60,000 pounds per square 
inch. 

Ques. Is a boiler stronger when generating 
steam than when cold? 

Ans. Yes; the tensile strength of iron and steel 
increase slightly up to a temperature of about 600 
degrees F., but above 600 degrees it becomes weaker 
very rapidly. No part of a clean boiler, when in 
service, can ever attain so high a temperature, so 
a boiler is about 2 per cent, stronger when hot than 
cold. 

Ques. What do you understand by the 
elongation of a boiler plate? 

Ans. It is the amount that a plate will stretch 
before breaking. A good boiler plate should have 
an elongation of about 22 per cent. 



PRACTICAL ENGINEERING 



27 



Ques. Define the term elastic limit ? 

Ans. The elastic limit of a substance is the greatest 
strain it will endure and still completely spring back 
when released. 




00 

2o 



k 



-w 



-3to6- 



V 



J 



/U~_ 



8" 



^j\ 



16"to 20" 



V 



^-I'Raoius 



J 






■* — 3T.6-- ■*» 



Figs. 8 to 10. — Test specimens for boiler construction. Fig. 8. — Specimen 
for iron plate; figs. 9 and 10, specimen for steel. 



Ques. Give principal dimension of a 70" x 16' 
horizontal boiler ? 

Ans. The shell plates in a boiler of this size should 
be 3/g inch thick, the heads should be Y2 inch thick 
and made of the best flange steel, the tubes would be 
about J/g inch thick. There will be about seventy 3- 
inch tubes. 



28 AUDELS ANSWERS ON 

Ques. This being the case, why are the heads 
of boilers built of heavier steel than the shell? 

Ans. The heads are made heavier because they 
are flat and the pressure tends to bulge them out ; the 
shell being round, is self supporting; that is, the 
pressure does not tend to change the shape of shell. 

Ques. What is flange steel? 

Ans. Steel that will stand flanging without weak- 
ening. 

Ones. Why is it possible to make boiler tubes 
so much thinner than shell plates and heads, 
though they are exposed to the same pres- 
sure? 

Ans. As the surface exposed to the pressure is 
very much less they are sufficiently strong although 
much thinner. 

Ques. Describe fully the method of securing 
boiler tubes in the tube sheets or heads. 

Ans. The holes are drilled in the tube sheets to 
receive the tubes loosely; the diameter of the tube 
ends is now increased by the roller expander, which 
is a frame carrying three steel rollers which may 
be forced against the inside of tube by driving a 
tapered mandril into frame. No particular skill is 
necessary to use an expander, but great care must 



PRACTICAL ENGINEERING 29 

be taken not to roll the tube too much, as that will 
expand the hole in tube sheet as well as the tube, 
and will cause leakage and no end of trouble. 

Ques. What is the difference between boiler 
tubes and wrought iron pipe? 

Ans. Boiler tubes lap welded, or drawn are 
measured from the outside. Pipe, as a general 
thing, is rolled and has a seam; pipe is always meas- 




Fig. 11. —Roller tube expander for expanding boiler tubes. 

ured from the inside. The sizes as listed do not corre- 
spond exactly to the actual sizes, especially for the 
smaller pipes. 

Ques. How strong are riveted joints in 
modern boilers as compared to the strength of 
boiler plates? 

Ans. A single riveted seam is 56 per cent, as 
strong as the solid plate; a double riveted, 70 per 
cent., and a triple riveted seam will have 85 per cent, 
the strength of the solid plate. This only holds 
true if the rivets are of proper size and properly 
pitched. 



30 AUDELS ANSWERS ON 

Ques. What is meant by the shearing 
strength of the rivets? 

Ans. It is the amount of strain in pounds applied 
to the rivet at right angles to its length that causes 
it to shear in half. 

Ques. What should be the tensile strength 
of rivets? 

Ans. From 50,000 pounds to 60,000 per square 
inch. 

Ques. What is meant by the pitch of rivets? 

Ans. The distance from the center of one rivet 
to the center of the next. 

Ques. What should be the pitch of a single 
riveted seam? 

Ans. For single riveted work the pitch should be 
about 2Ji times the diameter of rivet hole. 

Ques. What should be the pitch for double 
riveted work? 

Ans. About 3 times the diameter of rivet hole. 

Ques. How much larger should rivet hole be 
than rivet? 

Ans. The rivet hole should be about i 6 inch 
larger than rivet, because all rivets are driven hot, 
and if they would fit the holes snugly when cold they 
would not enter at all when red hot, as heat expands 
them. 



PRACTICAL ENGINEERING 



31 




Figs. 12 to 15. — Various forms of riveted joint: fig. 12, single riveted lap 
joint ; fig. 13, double riveted lap joint ; fig. 14, triple riveted lap 
joint; fig. 15, triple riveted butt joint with double butt straps. 



32 AUDELS ANSWERS ON 

Ques. Does riveting alone make a tight 
joint? 

Ans. No; all riveted joints must be calked, which 
is done with a round nosed tool with which the edge 
of upper lap of point is driven close against lower lap. 

Ones. What seams on a horizontal return 
tubular boiler are double riveted? 

Ans. The seams running lengthwise are double 
riveted, while the seams running around the boiler 
are single riveted. 



i 



^ J=^f^ 



UZ7 



1 \ 



Figs. 16 and 17. — Square and round nosed caulking tools; the latter is usually- 
employed in modern practice. 

Ones. If the seams running in the direction 
of the length of boiler be triple riveted, would 
the seams running around the boiler be double 
riveted ? 

Ans. No; the seams running around the boiler 
are always single riveted. 

Ques. Why? 

Ans. Because the strain on the seams running 
lengthwise is always much greater than on seams 
running around boiler. 



PRACTICAL ENGINEERING 33 

Ques. How do we find the load on a girth 
seam (seam running around boiler) of a hori- 
zontal tubular boiler? 

Ans. By multiplying the area of one head less 
the area of the tube ends in square inches by the 
pressure. 

Ques. How do we find the strain on each 
rivet in the girth seam? 

Ans. By dividing the strain on the seam by the 
number of rivets in the seam. 

Ques. How do we find the load on the longi- 
tudinal seam (the seam running lengthwise) of 
a horizontal tubular boiler? 

Ans. By multiplying the circumference of the 
boiler by the length of the boiler in inches and by 
the pressure; this last product is divided by two 
and the answer is the strain on the longitudinal 
seam. 

Ques. How do we find the load on each rivet 
in the longitudinal seam ? 

Ans. By dividing the strain on the seam by the 
number of rivets in the seam. 

Ques. Explain fully a lap joint and a butt 
strap joint? 

Ans. A lap joint on a boiler is one where one 
part of the shell plate laps over the other, hence the 



34 



AUDELS ANSWERS ON 



name. Lap joints are always used in single riveted 
work. A butt joint is a joint where the end of plates 
butt together and is made by riveting a strip of iron 
over the joint. Butt joints are used in double and 
triple riveted work. Some butt joints are made with 
a strip on both inside and outside of boiler; this 
makes a stronger job, because the rivets on a joint of 
this kind are in double shear. 




Fig. 18. — Steam dome of a horizontal boiler; its object is to secure steam with 
as little moisture as possible. The dome is cylindrical, having usually a 
flat plate top securely braced as shown. In the absence of a steam dome 
the boiler should be provided with a so called dry pipe, as shown in fig. 19. 



Ques. If a horizontal boiler have a dome, 
what seams of dome should be double riveted? 

Ans. The seam which secures dome to boiler shell. 



Ques. In an upright or vertical boiler, which 
seams should be double riveted ? 

Ans. The vertical seams. 



PRACTICAL ENGINEERING 



35 



Ques. In a horizontal tubular boiler, what 
part of boiler requires to be braced or stayed ? 

Ans. The space above the tubes on front and rear 
head. 

Ques. How much of this space must be 
supported ? 

Ans. To find the space that requires bracing, 
draw a line three inches above the top row of tubes 




zzn 



u^ 



X3 



Fig. 19. — "Dry pipe" for horizontal boiler; it is connected to the main outlet 
and its upper surface is perforated with small holes, the far end being closed. 
With this arrangement steam is taken from the boiler over a large area, so 
that it will contain very little moisture. A 11 horizontal boilers without a dome 
should be fitted with a dry pipe; most engineers do not realize the importance 
of obtaining dry steam for engine operation. 



across the boiler head and a line three inches below 
the curve of the flange all around upper part of head. 
This will give the space to be braced, its shape being 
a segment. 

Ques. How do we find the load on this seg- 
ment? 

Ans. By multiply ng its area in square inches by 
the pressure. 



36 AUDELS ANSWERS ON 

Ques. How do we find the area of this space, 
approximately? 

Ans. Multiply the distance from the upper row 
of tubes to top of boiler in inches by the distance 
across head of boiler three inches above the upper 
row of tubes; multiply the product by .7854 and 
the answer will be the area of segment very 
nearly. 

Ques. How would you find the number of 
one inch braces required in a certain boiler? 

Ans. By multiplying the area of the segment 
above the tubes in square inches, by the pressure in 
pounds, and dividing the product by 7,000. Answer 
will be the number of braces required. 

Ques. Do horizontal boilers ever require 
bracing below the tubes? 

Ans. Only large boilers. Where the distance 
between the lower tubes and bottom of boiler is 
considerable, these boilers are generally provided 
with two through stays running parallel to tubes from 
front head to rear head. 

Ques, What is the safe allowable stress on 
braces or stays? 

Ans. 7,000 pounds per square inch of area for 
iron braces. 



PRACTICAL ENGINEERING 



37 



IesKs 




• «FN 









Pigs. 20 to 29. — Various braces and stays. A, head brace; B, angle Iron 
stays; C, screw stay; D, riveted stays for fire box; E, vertical bar stays 
secured by nuts and washers to the crown sheet, and by pins to the boiler 
shell; F, roof stay; G, end braces; H, screwed longitudinal brace; I, gusset 
stay; J, palm stay. 



38 AUDELS ANSWERS ON 

Ques. Does the cutting of a manhole in head 
or shell of boiler weaken it? 

Ans. Yes, and this weakness is remedied by 
riveting a heavy iron ring around hole on the inside ; 
this ring should have a strength equal to the metal 
cut away to form the hole. 

Ques. How should large pipes be attached to 
boilers? 

Ans. For pipes above 1^ inches a plate should 
be riveted to shell at the hole; for pipes above 2 Y^ 
inches a cast iron flange nozzle should be riveted on 
boiler. 

Ques. What do you understand by a factor 
of safety of 6? 

Ans. The term factor of safety signifies the ratio 
between a working stress and a breaking stress. 
Thus, a boiler is said to have a factor of safety of 
six when the bursting pressure is six times the work- 
ing pressure. 

Ques. How do we find the bursting pressure 
of a horizontal tubular boiler? 

Ans. By multiplying the tensile strength of the 
weakest plate by its thickness in inches, and multi- 
plying the product by .56, for single riveted seams, 
by .70 for double riveted seams, or by .85 for triple 
riveted seams; divide this last product by one-half 
the diameter of boiler in inches, and the answer will 
be the bursting pressure. 



PRACTICAL ENGINEERING 39 

Ques. A boiler is 60 inches in diameter; 
plates are % inches thick, and have a tensile 
strength of 60,000 pounds per square inch; 
efficiency of longitudinal seam, 70% What is 
its bursting pressure? 

Ans. 60000 X 3 X .70 

= 525 lbs. 

8 X 30 
Solution: 

1st Step. 



X3 


30 


3rd Step. 

) 15750 (525 lbs. bursting 
150 pressure 

75 

60 

150 
150 


180000 
X.70 


126000 

2nd Step. 

8 ) 126000 



15750 

A boiler of the above dimensions would burst under 
a pressure of 525 pounds per square inch. 



40 AUDELS ANSWERS ON 

Ques. When the steam gauge registers 80 
pounds, what do you understand? 

Ans. That a pressure of 80 pounds is exerted on 
every square inch of surface inside the boiler on head, 
shell and tubes. 

Ques. How do we find the safe working press- 
ure of a horizontal tubular boiler? 

Ans. Multiply one-sixth of the lowest tensile 
strength found stamped on any pate in the cylindrical 
shell by the thickness (expressed in inches or parts of 
an inch) of the thinnest plate in the same cylindrical 
shell and divide by the radius or half diameter (also 
expressed in inches), the quotient will be the pressure 
allowable per square inch of surface for single riveting, 
to which add twenty per centum for double riveting 
when all the rivet holes in the shell of such boiler have 
been "fairly drilled" and no part of such hole has been 
punched ( U. S. rule). 

Ques. Do boiler inspectors depend entirely 
on this rule? 

Ans. No; they have what they call a hammer 
test and a hydrostatic test. 

Ques. How is a hammer test made? 

Ans, By striking all parts of the boiler inside 
and without, which are liable to fracture, crack or 
burn, a sharp blow with a light hammer; any loose 



PRACTICAL ENGINEERING 41 

rivets, cracked plates, etc., are at once found by an 
experienced inspector, being betrayed by the sound of 
hammer. 

Ques. What is one boiler horse power? 

Ans. One boiler horse power is equal to 34^" 
pounds of water evaporated per hour from a feed- 
water temperature of 212 degrees Fahr. into dry 
steam of the same temperature. The standard is 
equivalent to 33,317 British thermal units per hour. 
It is also practically equivalent to an evaporation of 
30 pounds of water from a feed-water temperature of 
100 degrees Fahr. into steam at 70 pounds gauge- 
pressure. 

A boiler rated at any stated capacity should develop that 
capacity when using the best coal ordinarily sold in the market 
where the boiler is located, when fired by an ordinary fireman, 
without forcing the fires, while exhibiting good economy; and 
further, the boiler should develop at least one-third more than 
the stated capacity when using the same fuel and operated by 
the same firemen, the full draft being employed and the fires 
being crowded; the available draft at the damper, unless other- 
wise understood, being not less than one-half inch water column. 

Ques. Give a rule that is much used, al- 
though it is only approximate? 

Ans. To find the horsepower of horizontal tubu- 
lar boiler we find the heating surface in shell tubes 
and both heads and divide by 15. That is, 15 square 
feet of heating surface are necessary for each horse 



42 



AUDELS ANSWERS ON 



power. Now only two-thirds of the shell is exposed 
to the heat, so we find the area of the shell and 
multiply by two thirds ; two thirds of the back head is 




Fig. 30. — Dimensions of standard vertical boilers; the letters refer to dimen- 
sions given in the table on page 43. Where sufficient head room is available, 
the vertical boiler makes a cheap construction and one which gives good 
economy when properly proportioned. The furnace is within the shell as in the 
case of the locomotive boiler, and a door is opened through the furnace wall 
and the boiler shell, which are joined together at this point. One advantage 
of this type of boiler is that it gives slightly superheated steam instead of 
slightly wet steam, as in the case of the horizontal boiler. If engineers were 
careful to always carry the water at the proper level, there would be no 
danger of burning the tubes; submerged tubes in vertical boilers are not 
necessary for long life when the boiler is properly proportioned and properly 
handled. 



PRACTICAL ENGINEERING 



43 



exposed to the heat, so we find the area of that part of 
head, and the full area of the front head; from each 
subtract the area of the tube ends; all the tube 
surface is heating surface, and we now add these 
three quantities together for the total heating surface 
in boiler and divide by 15 for the horse power. 



DIMENSIONS OF STANDARD VERTICAL BOILERS. 





Shell. 




Furnace. 




2-in. Tubes. 




















cUPh 






bo 43 
u 


s 


o 

Ph 
(D 
W 

u 
o 

H 


a 

s 






i 

Q 


i 


o 


J3 

■a 


6 


A 


B 


c 


D 


E 


F 


G 


H 




J 




Ins. 


Ft. 


Ins. 


Ins. 


Ins. 


Ins. 


Ins. 


Ins. 




S. Ft. 


Ins. 


4 


24 


4 


X 


20 


24 


Va 


# 


24 


31 


44 


12 


5 


24 


5 


Va 


20 


24 


32 




36 


31 


60 


12 


6 


24 


6 


Va 


20 


24 






48 


31 


75 


12 


8 


30 


5 


Va 


25 


27 






33 


55 


92 


14 


10 


30 


6 


Va 


25 


27 


A 




45 


55 


121 


14 


12 


30 


7 


Va 


25 


27 






57 


55 


150 


14 


15 


36 


6K 


Va 


31 


28 






51 


77 


189 


15 


18 


36 


7 


Va 


31 


28 






57 


77 


210 


15 


20 


36 


8 


Va 


31 


28 






69 


77 


250 


15 


25 


42 


7K 


3 9 5 


37 


30 






60 


109 


307 


18 


30 


42 


8K 




37 


30 






72 


109 


364 


18 


35 


42 


9K 


41 


37 


30 




A 


84 


109 


422 


20 


40 


48 


sy 2 


T6 


43 


32 






72 


149 


496 


24 


45 


48 


9 




43 


32 






78 


149 


535 


24 


50 


48 


10 


" 


43 


30 






90 


149 


613 


24 


60 


54 


9 




48 


30 






78 


201 


716 


28 



Ques. Can the horse power of a boiler be 
calculated by the grate surface? 

Ans. Yes, and this rule is about as accurate as 
the previous one just given and much simpler. 
Divide the grate surface in sq. ft. by the particular 



44 



AUDELS ANSWERS ON 



value of grate per horse power corresponding to the 
conditions of operation as given in the table below. 



Good coal and 
boiler 

Fair coal and 
boiler 

Poor coal and 
boiler 



Lbs. of water 

from and at 

212° F. per 

lb. coal. 


Pounds of coal burned per sq. i 
of grate per hour. 


t. 


15 1 20 I 25 | 30 | 35 | 40 


Sq. ft. grate per horse power. 


/ 10 


.23 


.17 


.14 


.11 


.10 


.09 


I 9 


.25 


.19 


.15 


.13 


.11 


.10 


( 8 


.29 


.22 


.17 


.14 


.13 


.11 


I 7 


.33 


.24 


.20 


.17 


.14 


.12 


( 6 


.38 


.29 


.23 


.19 


.17 


.14 


1 5 


.46 


.35 


.28 


.23 


.22 


.17 



In general allow y z sq. ft. of grate per horse power. 



Ques. How much water will the average 
boiler evaporate per hour? 

Ans. About 30 pounds, or about 3J/2 gallons for 
every horse power per hour. 

Ques. Which has the most surface, shell or 
head? 

Ans. The shell. 

Ques. How many times as much heating 
surface as grate surface will the average boiler 
have? 

Ans. The average boiler will have about 35 times 
as much heating surface as grate surface. 



PRACTICAL ENGINEERING 45 

Ques. How many pounds of coal can be 
burned per hour per square foot of grate sur- 
face? 

Ans. With natural draught about 14 pounds. 

Ques. How much coal will the average boiler 
burn per horse power? 

Ans. The average boiler will burn about four 
pounds of coal per hour per horse power. 

Ques. Define " heating surface." 

Ans. That surface exposed to the fire and hot 
gases; with respect to the tubes of a boiler it consists 
of the inner surface in a fire tube boiler and the outer 
surface in a water tube boiler. 

It is the common practice of boiler makers to use the external 
instead of the internal diameter of fire tubes, for greater con- 
venience in calculation, the external diameter of boiler tubes 
usually being made in even or half inches. This is an error and 
gives more than the true amount of heating surface. The pur- 
chaser should therefore note this fact where the builder agrees 
to furnish a given area of heating surface. 



46 AUDELS ANSWERS ON 

WATER TUBE 
BOILERS 



Ques. What is a water tube boiler? 

Ans. A type of boiler in which the water is inside 
the tubes instead of around the tubes, as in the hori- 
zontal boiler. The latter is sometimes spoken of as 
a fire tube boiler. 

Ques. Are many water tube boilers in use? 

Ans. Yes; next to the horizontal tubular, there 
are more horizontal water tube boilers in use to-day 
than all other types put together, for stationary 
work. 

Ques. What advantages are claimed for the 
water tube boiler? 

Ans. They are quick steamers, and may be built 
in units of 500 horse power and over ; they are easily 
transported, when built in sections. They are sup- 
ported independent of any brickwork, and have no 
riveted joints over the fire; the bulk of the heating 
surface is composed of thin tubes right in the fire; 
water tube boilers are also free from disastrous explo- 
sions. They are suited to very high steam pressures. 



PRACTICAL ENGINEERING 47 

Ques. What are the disadvantages of the 
water tube boiler? 

Ans. They contain less steam and water space, 
and while they steam quickly, they require a steady 
fire to keep the steam pressure constant, on account 
of the small water space; the water level falls very 
rapidly when boiler is worked up to its capacity, and 
feed is interrupted. 

Ques. Give a brief description of one make 
of water tube boiler? 

Ans. The Babcock & Wilcox boiler is composed of 
lap welded wrought iron tubes, placed in an inclined 
position and connected with each other, and with a 
horizontal steam and water drum, by vertical pas- 
sages at each end, while a mud drum is connected to 
the rear and lowest point in the boiler. The end 
connections are in one piece for each vertical row of 
tubes, and are of such form that the tubes are 
"staggered" (or so placed that each row comes over 
the spaces in the previous row). The holes are 
accurately bored out to size, and the tubes fixed 
therein by an expander. The sections thus formed 
are connected with the drum, and with the mud- 
drum also by short tubes expanded into bored holes, 
doing away with all bolts, and leaving a clear passage 
way between the several parts. The openings for 
cleaning opposite the end of each tube are closed by 



48 AUDELS ANSWERS ON 

hand hole plates, the joints of which are made in the 
most thorough manner, by milling the surfaces to 



Fig, 31. — The Babcock and Wilcox water tube boiler. One side of the brick 
seating has been removed to show the arrangement of the water tubes and 
furnace. TT, inclined tubes; SS, down flow tubes; UU, up flow tubes; F, 
furnace; B, mud drum; A, side wall; D, end wall; E, cleaning door. 



accurate metallic contact, and are held in place by 
wrought iron forged clamps and bolts. They are 
tested and made tight under a hydrostatic pressure 



PRACTICAL ENGINEERING 



49 




Fig. 32. — The Roberts marine water tube boiler with casing removed to show 
construction. This boiler consists of the following essential parts: 1, the 
steam and water drum; 2, lower drums (large horizontal pipes) ; 3, up flow 
coils made up with return bends; 4, large down flow pipes; 5, feed water 
heating coils (on each side of steam drum); 6, superheating coils running 
down on each side of the furnace. There are no special pipe fittings used 
in this boiler. It is tested to 500 or 600 lbs., and is good for a working pres- 
sure of 300 lbs. of steam. 



50 



AUDELS ANSWERS ON 



of 300 pounds per square inch, iron to iron, and with- 
out rubber packing, or other perishable substances. 

The steam and water drums are made of flange 
iron or steel, of extra thickness, and double riveted. 
They can be made for any desired pressure, and are 



f" 


r 2 ' 


^ ' 
^ V 






■:-"-".-:-:-:-: 




\ -:-: :-:-:-: 


if 


■ i 


kj 


,:V-: 
"A*. 





Fig. 33. — Principle of circulation in water tube boilers. The water in the tube 
directly above the fire is heated in excess of that in the other tube ; it expands 
and becomes lighter than the water in the tube to the right, resulting in a 
movement of the water as indicated by the arrow. The tube at the left, 
directly exposed to the fire, is called the up flow tube, as distinguished from 
the one (to the right) more remote from the fire, which is called the down flow 
tube. In the actual boiler, there is a large number of up flow tubes of small 
diameter and a few down flow tubes, usually of larger diameter. 



always tested at 50 per cent, above the pressure for 
which they are constructed. The mud drums are of 
cast iron, as the best material to withstand corrosion, 
and are provided with ample means for cleaning. 



PRACTICAL ENGINEERING 51 



THE STEAM GAUGE 



Ques. How can we tell what pressure is on 
a boiler? 

Ans. By the steam gauge. 

Ques. How does a steam gauge work? 

Ans. A steam gauge works on one of two princi- 
ples as shown in figs. 34 and 35. In the one class, 
the pressure of the steam acts upon diaphragms or 
plates of some kind, shown in fig. 35, which repre- 
sents a section of a pair of metal plates, A A, of this 
kind. These are made with circular corrugations, as 
shown in section and also by the shading. The steam 
enters by the pipe, c, and fills the chamber between 
the metal plates or diaphragms. The corrugations of 
the latter give them sufficient elasticity, so that when 
the pressure is exerted between them they will be 
pressed apart by the steam. If they were flat, it is 
plain that they would not yield, or only to a very 
slight degree, to the pressure of the steam. 



52 



AUDELS ANSWERS ON 



In the other class of gauge, the steam acts upon a 
bent metal tube of a flattened or elliptical section, such 
as shown in fig. 34. The pressure has a tendency to 
straighten this tube, and this straightening tendency 
is directly proportioned to the pressure; the free end 
of this tube is connected through suitable gearing to 




FlGS. 34 and 35. — Bent tube and diaphragm of corrugated metal as used in 
the two classes of steam gauge. 

the pointer or hand and moves same round the grad- 
uated dial. 

Ones. How can the accuracy of a steam 
gauge be tested? 

Ans. When the gauge is in good working order, 
the index or pointer moves easily with every change 
of pressure in the boiler, and if the steam be shut off 
from the gauge, the index should always go back to 0. 
In order to determine the accuracy of its indications^ 
however, it should be tested with a column of mercury. 



PRACTICAL ENGINEERING 



53 



Ques. What precaution is taken to prevent 
the steam taking the temper out of the discs 
or tubes of steam gauges? 

Ans. They are put on with a turn or two of pipe 
between the boiler and the disc ; the bend of the pipe 
gradually filling with condensed steam, which pre- 
vents the live steam touching the elastic discs 
or tubes. 




Figs. 36 to 38. — Various forms of connection for steam gauge. The pocket 
formed by the connection becomes filled with water of condensation which 
protects the spring from the heat of the steam. 



Ques. What kind of pressure does a steam 
gauge indicate? 

Ans. It shows, what is called the gauge pressure, 
as distinguished from absolute pressure; that is, 
pressure measured above the atmospheric pressure, 
instead of above a perfect vacuum, as in the case of 
absolute pressure. 



54 AUDELS ANSWERS ON 

Ques. To what should the hand of the 
steam gauge point when there is no pressure 
in the boiler? 

Ans. To 0, or zero. 

Ques. Does this indicate that the gauge is 
correct? 

Ans. No; if it point to a figure above 0, it is cer- 
tainly out of order; but the fact of its pointing to 
when there is no pressure does not prove its correct- 
ness even at low pressures ; it might continue pointing 
to when there was pressure on it ; or it might point 
to 90 when there was 100 pounds pressure on it, and 
to 160 when there was 170 pounds. Gauges may be 
" fast " at some steam pressures, and " slow " at 
others. 

Ques. Which it the more dangerous gauge: 
one that is "fast" or one that is "slow." 

Ans. One that is slow. 



PRACTICAL ENGINEERING 



THE SAFETY VALVE 



Ques. What is the most important valve on 
any type of boiler? 

Ans. The safety valve. 

Ones. What is the object of the safety valve? 

Ans. To prevent the steam raising above the safe 
working pressure or above the pressure at which it 
is set. 

Ques. What care should a safety valve 
receive? 

Ans. It should be kept clean and should be raised 
by hand every morning. 

Ques. Why should it be raised so often? 

Ans. So that it cannot stick in its seat through 
the accumulation of dirt and scale. 

Ques. Can you give a rule to find the ap- 
proximate size of safety valve for a given size 
boiler? 

Ans. Yes ; allow one square inch of area of valve 
to every two square feet of grate surface. 



56 AUDELS ANSWERS ON 

Ques. What may be said of the above rule? 

Ans. It gives about the right area for low pressure 

boilers (25 to 50 lbs., working pressure), but too 

much for medium, or high pressure boilers. The 

rule has been enforced by law in some districts, for 

convenience of calculation and to clearly define the 

requirements. 

For calculations of precision, it should be noted that the grate 
area alone is no criterion in determining the correct size of safety 
valve. The proper area of opening depends on the weight of steam 
to be blown off per minute and the working pressure. The grate area 
is simply one of many factors which enter into the calculation 
of total capacity. Thus, to determine the weight of steam gen- 
erated per minute, it is necessary to consider in addition to the 
grate area, the kind and quality of fuel, rate of combustion, 
efficiency of the heating surface, pressure, etc. 

Ones. Give a better rule for proportioning 
the safety valve. 

Ans. The area of opening should be such, that 
when the boiler is worked at its maximum capacity 
the steam may escape, as fast as it is generated, at a 
velocity of not over 6,000 feet per minute at the 
working pressure, and before expansion. 

Ques. What types of safety valve are in 
general use? 

Ans. The lever safety valve, and the spring 
safety valve. 

Ques. How should a safety valve be attached 
to boiler? 

Ans. It should be attached to a separate outlet, 
but if only one outlet be on boiler it may be attached 



PRACTICAL ENGINEERING 



57 



to a tee on main steam pipe, as close to boiler as 
possible without any kind of valve between it and 
boiler. 

Ques. How is the pressure regulated on the 
weight and lever safety valve? 

Ans. By moving the weight on lever; the farther 
it is from valve the greater the blowing off pressure. 




Fig. 39. — A pop safety valve. To insure proper working, the valve should be 
attached directly to the boiler, otherwise the discs are likely to give trouble 
by chattering. Pop valves should be operated at least once a day, which 
will overcome any tendency of sticking. For superheated steam, a valve 
with outside spring should be used. 

Ques. How is the blowing off pressure reg- 
ulated on a spring loaded valve? 

Ans. By increasing or decreasing the tension of the 
spring. This style of valve always has an adjusting 



58 AUDELS ANSWERS ON 

spindle, and by compressing the spring we increase 
the blowing off pressure, by slacking tip on spring 
we decrease it. 

Ques. Why does a pop safety valve "pop" ? 

Ans. In this type of spring valve, the construction 
is such that as soon as the valve begins to open an 



CENTER OF 
GRAVITY 



Fig. 40.— Method of finding the center of gravity of the lever. The center of 
gravity of the lever is the point where the bar would be in equilibrium if 
balanced over a knife edge or any other support with a sharp corner, as 
shown in the figure. 

excess area of the disc is presented to the escaping 
steam, hence it suddenly opens widely. 



Ques. What is the peculiar feature in the 
operation of a pop valve? 

Ans. It will continue to blow until the pressure 
is reduced somewhat below that at which it opens. 



PRACTICAL ENGINEERING 59 

Ques. Why is this? 

Ans. It is due to the increased area of disc presented 
when the valve opens. 

Ques. What type of spring valve should be 
used with superheated steam? 

Ans. One with an outside spring. 



SAFETY VALVE RULES 

Rule for finding the weight necessary to put on a safety 
valve at a given distance from the fulcrum, so that the 
valve will blow at a given pressure. 

1. — Find the area of the valve, in inches, by squaring the 
diameter of the opening and multiplying the product by .7854, 

2. — Multiply the area thus found by the steam pressure on 
the boiler. 

3. — Deduct from the product the weight of the valve and stem. 

4. — Multiply the weight of the lever, in pounds, by the dis- 
tance of its center of gravity, in inches, from the fulcrum, and 
divide this by the distance from the valve center to the fulcrum, 
and deduct the quotient from the remainder found according to 
Section 3. 

5. — Multiply the last result by the distance of the valve (a) 
from the fulcrum and divide the product by the length of the 
lever. 

The answer is the weight of the ball to be placed at the end 
of the lever to balance the required pressure of steam. 



60 



QUDELS ANSWERS ON 




PRACTICAL ENGINEERING 61 

Rule for finding the steam pressure at which a valve 
will blow for given position and weight of ball. 

1. — Multiply the weight of the ball in pounds, by its distance 
in inches from the fulcrum, and divide the product by the dis- 
tance in inches, between the fulcrum and the center of the 
valve (a). 

2. — Multiply the weight of the lever in pounds, by the dis- 
tance in inches, of its center of gravity from the fulcrum and 
divide the product by the distance in inches of the fulcrum, from 
the center of the safety valve (a). 

3. — Add to the two results already obtained (Sections 1 and 
2) the actual weight of the valve and spindle; the sum of the 
three numbers will equal the downward pressure on the valve. 

4. — Now, obtain the area of the valve by squaring its diameter 
and multiplying by the decimal .7854. 

5. — Divide the total downward pressure (Section 3) by the 
area of the valve (Section 4) and the answer will be the total 
steam pressure per square inch on the boiler. 

Rule for finding the distance from the fulcrum at 
which the ball should be placed so that the valve will 
blow at a given pressure. 

1. — Multiply the area of the valve in square inches, by the 
pressure in pounds per square inch, at which it is required to 
blow; deduct from the product the weight in pounds of the 
spindle and valve. (Call this Section 1.) 

2. — Multiply the weight of the lever, in pounds, by the dis- 
tance, in inches, of its center of gravity from the fulcrum ; divide 
this product by the distance in inches from the center of the 
valve to the fulcrum. (Call this Section 2.) 

3. — Deduct amount obtained by calculations in Section 2 from 
that obtained in Section 1 ; this remainder is the pounds pressure 
on the valve which must be balanced by the ball. 



62 AUDELS ANSWERS ON 

4. — Multiply this last "remainder" by the distance in inches 
between the valve center and the fulcrum, and divide the product 
by the known weight of the ball in pounds. The result will be 
the required distance, in inches, of the weight (or ball) from the 
fulcrum. 



There are two methods by which the applicant for 
an engineer's license can prepare to answer questions 
on the safety valve problem: 1, by learning several 
rules parrot fashion, or 2, by reasoning out the matter 
and writing an equation from which the answer to 
any question the examiner may ask is easily obtained. 

The man who adopts the first method, spends con- 
siderable time in memorizing the several rules, which 
have absolutely no meaning to him, and consequently, 
he does not know any more about the problem than 
he did at first, although he may be able to recite these 
rules and pass the examination. 

Again, the man who can solve the problem by the 
second method understands what he is talking about; 
he knows why a given weight must be placed at a 
certain point for the valve to blow at a given pressure. 
Moreover, he commands respect rather than tolerance 
from the examiner. 



PRACTICAL ENGINEERING 63 

Unfortunately, those with very limited knowledge 
of mathematics are unable to learn how to construct 
and solve an equation without considerable study, but 
the author believes, in most cases, that the time spent 
in committing to memory meaningless rules, could be 
far better utilized in studying the principles of the 
problem and thus acquire some real knowledge rather 
than artificial knowledge. 

Principle of the Safety Valve. — When a boiler 
is in operation there are four forces acting on a lever 
safety valve, of which, one tends to raise the valve off 
its seat and the other three tend to' keep it closed; when 
the first force slightly exceeds the sum of the other 
three forces, the valve will open and allow the steam 
to escape. The four forces just mentioned may be 
described as follows: 

1. The force due to the steam, which tends to raise 
the valve; it is equal to the area of the valve in square 
inches multiplied by the steam pressure as indicated 
by the steam guage ; 

2. The force due to the weight of the valve and 
spindle, which tends to close the valve; 

3. The force due to the weight of the lever, which 
tends to close the valve; 

4. The force due to the weight of the ball, which 
tends to close the valve. 



64 AUDELS ANSWERS ON 

These forces act at different distances from a point 
called the fulcrum, which corresponds to the point F 
in fig. 42, about which the lever turns. As indicated 
in the figure, the four forces are as follows : 

S = total pressure due to the steam tending to raise 
the valve ; 

This is equal to the steam pressure indicated by the 
steam gauge multiplied by the area of the valve. The 
area of the valve is equal to its diameter squared, multi- 
plied by .7854. 

V = weight of valve and spindle; 
G = " " lever; 
B = " " ball. 

The distances at which these forces act are: 

v = distance from fulcrum to center of the valve ; 

g — a cen t er f gravity of 

the lever ; 
b = distance from fulcrum to the ball. 

The weights are measured in pounds and the distances in 
inches. 

The weight of the lever is considered as acting at its center 
of gravity, g distance from the fulcrum. 

The center of gravity of the lever is that point where it would 
be in equilibrium if balanced over a knife edge or any other 
support with an edge, as in fig. 40. 

Now, since all of these forces do not act along 
the axis or central point of the valve (fig. 42), 



PRACTICAL ENGINEERING 



65 



it is necessary to determine the tendency of the several 
forces to produce rotation of the lever about the fulcrum F. 

In order to determine this, the moments of the 
several forces with respect to the fulcrum F must be 
determined. 

In mechanics the moment of a force is a measure of 
its effect in producing rotation about a fixed point. 




Fig. 42. — Lever safety valve with dimensions, etc., necessary in making calcu- 
lations, b, Distance from fulcrum to ball; g, distance fulcrum to center of 
gravity of lever; v, distance fulcrum to spindle; F, fulcrum; V, weight of 
valve and spindle; G, weight of lever;' B, weight of ball. 

The moment of a force, with respect to a point, is the 
product of the force multiplied by the perpendicular dis- 
tance from the point to the direction of the force. 



The fixed point (corresponding to the fulcrum F) is called 
the center of moments, and the perpendicular distance, the lever 
arm or leverage of the force. 

The moment of the ball B in fig. 42 with respect to the 
fulcrum F, for instance, is equal to the weight of the ball multi- 
plied by its distance from F, that is, moment of the ball = B X b 
or simply Bb. 



66 AUDELS ANSWERS ON 

The four moments to be considered in solving the 
safety valve problem are as follows : 

1. Moment due to the steam; 

It is equal to the total pressure of the steam acting on 
the valve multiplied by the distance from fulcrum to 
center of valve; that is, in fig. 42, steam moment = Sv. 

2. Moment due to the weight of the valve and 
spindle ; 

It is equal to the weight of the valve and spindle multi- 
plied by the distance from fulcrum to center of valve; 
that is, valve and spindle moment = Vv. 

3. Moment due to the weight of the lever; 

It is equal to the weight of the lever multiplied by the 
distance from the fulcrum to the center of gravity of the 
lever; that is, lever moment = Gg. 

4. Moment due to the weight of the ball. 

It is equal to the weight of the ball multiplied by the 
distance from the fulcrum to the ball ; that is, ball moment 
= Bb. 

Now, when the valve is at the point of blowing off, 
the first moment which tends to raise the valve will equal 
the sum of the other three moments which tend to keep 
the valve closed; that is : 

steam \ ( valve and ] f lever ] f ball 

moment I _. J spindle moment 1 _i_ J moment 1 _j_ J moment 

SXv) [ VXv J [GXgJ [BXb 



PRACTICAL ENGINEERING 67 

or simply : 

Sv = Vv + Gg + Bb. 

Tfe ^s the safety valve equation with which any 
problem is easily solved. In working out an example, 
the given values are substituted for the letters and 
the equation solved for the unknown letter. 

EXAMPLE:— What weight ball must be put on a 3" safety 
valve so that it will blow at 100 lbs., if the weight of valve and 
spindle be 8 lbs., lever, 24 lbs., distance of valve from fulcrum 
4"; distance of center of gravity from fulcrum 16"; distance 
from fulcrum to ball 38". 

First write out the equation and substitute the values given 
in the example under the proper letters, thus: 

Sv = Vv + Gg + Bb 
SX4 = 8X4 + 24X16 + BX38 
multiplying 

4S = 32 + 384 + 38B 
and adding 

4S = 416 + 38B 

S, the total pressure tending to raise the valve is equal to the 
steam pressure multiplied by the area of the valve in square 
inches = 100 X diam. X diam. X .7854 = 100 X 3 X 3 X .7854 
= 706.9 lbs., say 707 lbs. 

Substituting this for S in the equation: 4S =420+38B thus: 

4 X 707 = 416 + 38B 
multiplying 

2828 = 416 + 38B 



68 



AUDELS ANSWERS ON 



The equation must be "solved for B," which means that 
everything must be transferred to the left hand side of the 
equality sign except the B. The first step then is to get the 416 
on the left hand side; to do this, subtract 416 from both sides, 
thus : 




Fig. 43. — Weighing the force exerted by the lever; by thus obtaining the 
downward thrust due to the lever, the calculation is simplified as explained 
on page 69. 



2828 = 416 +38B 
416 416 



2412= 38B 



As it now stands, 2412 =38B, or in other words, 38 B=2412 
hence ; 

2412 
B =-33- = 63.4 lbs., weight of ball. 



PRACTICAL ENGINEERING 



69 



When the engineer has to solve a safety valve prob- 
lem in actual practice, he may do so without finding 
the center of gravity of the lever, if he use a spring 
balance as in fig. 43. 

The balance should be hooked under the point at 
which the valve spindle acts and then by pulling up 
on the balance, the actual downward pressure of the 




Fig. 44. — Lever safety valve with dimensions, etc., necessary in making calcu- 
lations where the thrust due to the lever is determined by a spring balance 
as in fig. 43. b, distance fulcrum to ball; v, distance fulcrum to valve; 
M = S — L, that is, the total pressure due to the steam tending to raise the 
valve, less the downward thrust due to the lever as measured in fig. 43; 
F, fulcrum; B, weight of ball. 

lever at this point can be determined. To this weight 
should be added the weight of the valve and spindle. 

The forces then will be as in fig. 44, from which 
the equation is : 

St; = Mv + Bb 

here M is equal to the sum of the pressure of the lever 
as indicated on the scale and spring fig. 43, plus the 



70 AUDELS ANSWERS ON 

weight of the valve and spindle; the other letters are 
as before. 

If the weight of the ball, or its distance from the 
fulcrum be required, the equation can be still further 
simplified by letting M, in fig. 44, represent the sum 
of the pressure of the lever as indicated on the spring 
scale plus the weight of the valve and spindle, sub- 
tracted from the total pressure of the steam on the 
valve. The equation then becomes 

Mv = Bb 



PRACTICAL ENGINEERING 



71 



TABLE 



OP THE 

PROPERTIES OF SATURATED STEAM. 

From Peabody's Tables. 



a 
© — 
u . 

II 



43 j 

S3 
212.00 


« ea i • 

o 
H 
1146.6 


— 00 . 
g^ to 

» — T) 

K 
180.8 


-£•* . 

o 

p> 

a a - 
>— • 

X 
965.8 


• © Density of weight 
: " of 1 cu. ft. in 

• os lbs 

! o Volume of 1 lb. 

• 'a in cubic feet. . 


HI 

l-Kw • 

59.76 








59.64 


10 


239.36 


1154.9 


208.4 


946.5 


.06128 16.32 


59.04 


20 


258.68 


1160.8 


227.9 


932.9 


.08439 11.85 


58.50 


30 


273.87 


1165.5 


243.2 


922.3 


.1070 9.347 


58.07 


40 


286.54 


1169.3 


255.9 


913.4 


.1292 7.736 


57.69 


50 


297.46 


1172.6 


266.9 


905.7 


.1512 6.612 


57.32 


55 


302.42 


1174.2 


271.9 


902.3 


.1621 6.169 


57.22 


60 


307.10 


1175.6 


276.6 


S99.0 


.1729 5.784 


57.08 


65 


311.54 


1176.9 


281.1 


895.8 


.1837 5.443 


56.95 


70 


315.77 


1178.2 


285.6 


892.7 


.1945 5.142 


56.82 


75 


319.80 


1179.5 


289.8 


889.8 


.2052 4.873 


56.69 


80 


323.66 


1180.6 


293.8 


886.9 


.2159 4.633 


56.59 


85 


327.36 


1181.8 


297.7 


884.2 


.2265 4.415 


56.47 


90 


330.92 


1182.8 


301.5 


881.5 


.2371 4.218 


56.36 


95 


334.35 


1183.9 


305.0 


879.0 


.2477 4.037 


56.25 


100 


337.66 


1184.9 


308.5 


876.5 


.2583 3.872 


56.18 


105 


340.86 


1185.9 


311.8 


874.1 


.2689 3.720 


56.07 


110 


343.95 


1186.8 


315.0 


871.8 


,2794 3.580 


55.97 


115 


346.94 


1187.7 


318.2 


869.6 


.2898 3.452 


55.87 


120 


349.85 


1188.6 


321.2 


867.4 


.3003 3.330 


55.7.7 


125 


352.68 


1189.5 


324.2 


865.3 


.3107 3.219 


55.69 


130 


355.43 


1190.3 


327.0 


863.3 


.3212 3.113 


55.58 


135 


358.10 


1191.1 


329.8 


861.3 


.3315 3.017 


55.52 


140 


360.70 


1191.9 


332.5 


859.4 


.3420 2.924 


55.44 


145 


363.25 


1192.8 


335.2 


857.5 


.3524 2.838 


55.36 


150 


365.73 


1193.5 


337.8 


855.7 


.3629 2.756 


55.29 



72 



AUDELS ANSWERS ON 



INSTALLATION 
OF BOILERS 



Ques. How should a horizontal tubular boiler 
be set? 

Ans. On a good unyielding foundation. The side 
walls for a medium sized boiler should be about 16 




Fig. 45. — Boiler blocked up ready for setting. 

to 20 inches thick and should have an air space of 
about 2 inches the entire length, except that part of 
walls under the lugs, which should be built solid, 
like a pillar. The furnace should be lined with first 
quality fire brick, and it is well to extend the fire 



PRACTICAL ENGINEERING 73 

brick lining one or two feet back of bridge wall. 
All fire brick should be laid in fire clay, and the rest 
of setting should be built of hard, red brick, laid 
in lime or Portland cement. The rear wall should 
be about 16 inches thick, built entirely of red brick, 
except the arch over cleaning out door, which should 
be of fire brick. The front wall, for a flush front 
boiler, need only be about 12 inches thick. The jambs, 
and arch over furnace doors, should be most carefully 
built, as this part of furnace and furnace wall require 
frequent renewing. The bridge wall may be from 
16 to 24 inches thick, and should come to within 
about 9 or 10 inches of the lowest part of boiler. 

Ones. Should a horizontal tubular boiler 
be set exactly level? 

Ans. No. The back end should be from 1 inch 
to 1% inches lower than the front end, so that when 
we open up boiler for inspection or cleaning all the 
water will drain back to blow off outlet. 

Ques. Why should we provide for expansion 
in a boiler setting? 

Ans. A boiler when hot will be slightly longer 
than when cold, and provision must be made for this 
expansion or the setting will crack. 

Ones. What is a " dead plate "? 

Ans. A heavy cast iron plate placed in front of 
grates. 



74 



AUDELS ANSWERS ON 




PRACTICAL ENGINEERING 75 

Ques. What is an arch plate? 

Ans. It is a heavy cast iron plate reaching across 
front of boiler from jamb to jamb above the furnace 
door. Its object is to protect the brick work above 
the furnace door from the heat. 

Ques. What is the best kind of an arch to 
use above the furnace doors? 

Ans. A water arch, which consists of a hollow 
steel or cast iron chamber of such shape that it will 
fit between front and boiler all the way across furnace. 
The feed water is made to flow through this arch, 
and the arch is also connected with top and bottom 
of boiler to keep up the circulation when feed pump 
is closed down; this arch saves the cost of frequent 
repairs and also adds a little heating surface to the 
boiler. 

Ques. How are grate bars installed in boilers ? 

Ans. Heavy cast iron bars are run across the fur- 
nace near the dead plate and one near the bridge 
wall, on which the grates are laid. If the grates be 
over 4 feet long a center bearing bar should also be 
used. 

Ques. At what distance should the grates be 
from the lowest part of boiler? 

Ans. The grate bars should be about 24 inches 
below the lowest part of boiler for hard coal; for 



70 AUDELS ANSWERS ON 

soft coal, they should be placed about 28 inches 
below the lowest part of boiler. 

Ques. What is a mud drum? 

Ans. Horizontal boilers were formerly fitted with 
mud drums; a mud drum is a small pot or chamber 
riveted to bottom of back of boiler, into which the 
sediment and mud settled. Few horizontal boilers 
are built with mud drums, although several types of 
water tube boiler are fitted with them. 

Ques. What is a surface blow off? 

Ans. A pipe passing through front or rear head 
into the boiler at the water line fitted with a valve 
which may be opened daily, and through which the 
impurities in water floating on the surface may be 
expelled. 

Ques. How would you attach a blow off pipe 
to a boiler? 

Ans. I would attach blow off pipe to bottom of 
shell, near the back end of boiler and run pipe through 
the setting of boiler, as near the boiler as possible; 
I would attach a good, reliable cock and continue 
blow off pipe to tank or sewer. 

Ques. Should the blow off pipe between the 
boiler and setting be protected? 

Ans. Yes; it should be protected by a metal 
sleeve or wrapped with asbestos. A good plan is to 



PRACTICAL ENGINEERING 77 

connect the blow off pipe with both top and bottom 
of the boiler; in this case there is always a circula- 
tion in pipe, and it is less liable to burn out. 

Ques. Are you allowed to blow directly into 
sewers in New York City? 

Ans. No. The blow off should lead into a closed 
tank to break the force of the steam and water, and 
this tank may be connected with the sewer. 

Ques. How would you connect up the water 
column ? 

Ans. I would put the column at such a height so 
that the bottom of glass gauge would be two inches 
above the tops of the upper row of tubes on a small 
boiler and about six inches above the upper row of 
tubes on a very large boiler. 

Ques. How would you connect a feed pipe 
to a boiler? 

Ans. I would have the pipe enter boiler through 
the front head, about two inches above the upper row 
of tubes. Just outside of boiler I would put on a 
globe valve; then a short nipple and a check valve, 
and continue pipe to pump, where I would place 
another globe valve with which to regulate the water 
supply. 

Ques. What is a fusible plug? 

Ans. A fusible plug is a brass plug having a 
hole drilled all the way through. This hole is filled 



78 AUDELS ANSWERS ON 

with pure tin or other soft metal which melts at a 
temperature of about 600 degrees F. This plug is 
screwed into the back head on a horizontal tubular 
boiler as close to the top of the upper row of tubes as 
possible. Now, when the water is at its proper level, 
the temperature of plug cannot rise much above the 
water in boiler and the soft metal cannot melt, 
because the water will absorb the heat too fast; 
however, if the water in boiler should fall below the 
plug, it would immediately melt out, and the escaping 
steam and water would put out the fire. 

Ques. How should the main stop valve be 
attached to boiler? 

Ans. In such a way that the pressure will come 
under the valve ; a valve attached in this manner may 
be packed under pressure by closing the valve. 

Ques. How should large steam pipes be 
secured ? 

Ans. Large steam pipes should be secured to 
overhead beams or suspended from the roof in a most 
thorough manner. Violent vibration of large pipes 
will soon lead to leaks at the joints. 

Ques. Why do we put a check valve near 
boiler? 

Ans. So that no water can flow from boiler back 
to pump when pump is stopped. 



PRACTICAL ENGINEERING 79 

Ques. Why do we put a globe valve between 
check valve and boiler? 

Ans. So we can open up check valve for the 
purpose of inspection or repair while a pressure is 
on boiler by simply closing the globe valve between 
check valve and the boiler. 

Ones. Is a damper regulator a useful appli- 
ance? 

Ans. Yes, it assists in keeping the steam pressure 
constant. 

Ques. What should be the area of a chimney 
or stack? 

Ans. The area of a chimney should be about 30 
per cent, more than the combined area of all the 
tubes. 



80 AUDELS ANSWERS ON 

MANAGEMENT 
OF BOILERS 



Ques. What is the first duty of the engineer 
or fireman on entering the boiler room in the 
morning? 

Ans. To make sure that the water in boiler is at 
a proper level. 

Ones. If on entering the boiler room you 
would find the water out of glass, safety valve 
blowing off strong, and a good, hot fire under 
boiler, what should be done? 

Ans. First, the fire should be smothered as quickly 
as possible with wet ashes, earth or coal, closing ash 
pit doors and leaving furnace doors and damper open. 
If now it be found that the water has not fallen below 
the level of either the crown sheet of any other ex- 
tended area of heating surface, the feed pump may be 
started with perfect safety, but if this certainty cannot 
be assured, the boiler must be cooled down completely, 
carefully inspected, and repaired if necessary. If no 
part of the exposed metal be heated to redness, there 
is no danger except from a rise in the water level 
sufficient to flood the overheated metal. Hence, care 



PRACTICAL ENGINEERING 81 

should be taken that the safety valve be not raised 
so as to produce a priming that might throw the 
water over the overheated metal, and that no change 
be made in the working of either engine and boiler that 
shall produce priming or an increased pressure. 

If any portion of the boiler plate be red hot, an additional 
danger is due to the steam pressure, which should be reduced 
by continuing the engine in steady operation while extinguishing 
the fire. If the safety valve be touched at such a time it should 
he handled very cautiously, allowing the steam to issue steadily 
and in such quantity that the steam gauge does not show any 
sudden fluctuations while falling. The damping of the fire with 
wet ashes will reduce the steam pressure very promptly and 
safely. 

Ones. How should a boiler be fed? 

Ans. The pump should run constantly, supplying 
just enough water to keep the water line in boiler at 
a constant level. 

Ques. What is meant by priming? 

Ans. We say a boiler primes when it lifts the 
water level and delivers steam full of spray or water 
to engine. 

Ques. What is the cause of priming or 
foaming, as it is sometimes called? 

Ans. Priming is usually caused by forcing a 
boiler too hard or by too high a water level. Foam- 
ing is caused by dirty or impure water; in either 
case the remedy is to check the draught. When a 



82 AUDELS ANSWERS ON 

boiler primes violently it may be necessary to close 
the main steam valve for a few seconds to find the 
true water line. 

Ques. Would you fire a water tube boiler the 
same as a fire tube boiler? 

Ans. Yes. Strictly speaking, the work would be 
about the same. 

Ques. Why do we often see the fronts of 
boilers cracked and broken? 

Ans. When the brickwork over the furnace door 
becomes bad and is not quickly repaired, the front 
will become overheated and in a short time will 
crack. 

Ques. How are the hand holes and man holes 
cut in boilers? 

Ans. Crossways and oval in shape. 

Ques. How are the tubes of a horizontal 
boiler cleaned? 

Ans. The soot and ashes may be blown out with a 
steam blower or swept with an iron or steel wire 
brush. When a blower is used the steam should be 
dry, so as not to leave moisture on inside of tube, 
which will form a scale and, in some cases, will 
corrode the tube; all tubes should be swept at 
frequent intervals; the oftener the better. 



PRACTICAL ENGINEERING 83 

Ques. How is a crack between two tube holes 
in a boiler head repaired? 

Ans. By fitting an iron or steel patch over crack, 
which may be fastened with two tap bolts ; a layer of 
cement made of red lead and iron filings should be 
spread under the patch. 

Ones. If a tube should split or leak, how 
would we replace it? 

Ans. When boiler tubes have to be cut out, it is 
done by cutting a long slot in tube from front end; 
this slot should be cut with a ripping chisel and 
should extend back about 3 inches ; the tube may now 
be contracted and by cutting the back end loose, can 
easily be pulled out. A new tube is now inserted and 
secured into both heads with an expander and the 
ends of tube riveted over. 

Ques. What care do the various appliances 
of a boiler require? 

Ans. The safety valve should be kept clean and 
working freely by lifting by hand at least three times 
a week. The water column should be blown out 
every day and kept free from scale, when blowing 
down; the water should come up in glass rapidly, 
and if it do not, the lower connection is partly 
stopped up; the gauge should not be entirely relied 
upon, the gauge cocks should be tried frequently, 



84 AUDELS ANSWERS ON 

and in all cases the glass and cocks should agree, if 
they do not agree the cause should be found and 
removed. The steam gauge should agree with safety 
valve at the blowing off pressure, and should be con- 
nected to boiler through a trap or syphon, so that the 
water in tube of gauge will be comparatively cold; 
when steam is allowed to enter gauge directly it will 
draw temper out of tube and the gauge will not re- 
cord correctly. The feed pump or injector should 
be kept in perfect condition, and all globe valves and 
the check valve in feed pipe should be carefully kept 
in repair. The blow off should be opened once every 
day, preferably at the time of day when pressure is 
lowest, as this assists greatly in keeping a boiler clean 
and in prolonging life of boiler; the blow off valve 
should be kept tight and pipe kept covered inside of 
setting to protect it from the intense heat. If a 
fusible plug be used it must be kept clean within and 
without the boiler, otherwise it may not act when 
needed. 

Ques. What care do fusible plugs require? 

Ans. They must be kept clean on the outside, 
otherwise they will not melt out if water in boiler 
fall below the plug, and they must not be allowed 
to become covered with scale on the inside, or they 
may melt out, even when covered with water, through 
the inability of the water to absorb the heat through 
the scale. 



PRACTICAL ENGINEERING 85 

Ques. In case one of the fire plates of a 
boiler bagged or bulged over the fire, how would 
you repair it? 

Ans. If the plate was not burned, and not drawn 
thin, I would heat it red hot by rigging up a gas 
furnace under the bulge and drive it up into its 
original position. If the plate was burned or too 
large to drive back, the burned part must be cut out 
and a patch put on. A slightly bulged plate may be 
prevented from getting worse by putting a stay 
through the center of bulge and attaching the other 
end of stay to some part of boiler diametrically 
opposite. If a bulge, bag or blister be very large, or 
if the metal be wasted thin, a new fire sheet should 
be put in. 

Ques. In case of fire in building where you 
are employed, what would you do? 

Ans. I would haul the fire from under boiler, 
and, if a tank were on roof to supply fire lines, I 
would start the tank pump full speed and abandon 
the boiler room 

Ques. Suppose the fire had gained such head- 
way before discovery that you would not have 
time to haul fires, what would you do? 

Ans. I would open furnace doors, start feed 
pump and tank pump full speed and abandon boiler 
room. 



86 AUDELS ANSWERS ON 

Ques. If the burning building had its own 
electric light plant, would you stop dynamo 
engine before abandoning boiler room? 

Ans. No; I would leave engine running so as to 
keep up the lights, which may be of assistance to 
the tenants in leaving the burning building quickly. 

Ques. What about the elevator machinery? 

Ans. I would not stop the elevator machinery for 
same reason. 

Ques. How often should a boiler be cleaned ? 

Ans. This depends on the quality of the feed 
water, the kind of fuel, and conditions of operation. 
This cleaning should be done thoroughly, and, when 
opened up for cleaning, the engineer has an oppor- 
tunity to make a thorough inspection also. If any 
hard scale be present on the fire plates, heads or 
tubes, it should be removed with a scaling hammer, 
and all mud in bottom of boiler washed out. The 
braces should all be sounded to see if they be tight, 
for they are useless if slack. The tube ends on front 
and rear heads should be examined for leaks and all 
accessible seams should be carefully looked over. 
The brickwork should also be inspected. 

Ques. What causes scales to accumulate on 
the heating surface of boilers? 

Ans. As all water contains more or less solid 
matter, scale will form in all boilers; this solid 



PRACTICAL ENGINEERING 87 

matter forms a scum on the surface of the water, but 
finally becomes heavy enough to sink and is deposited 
and baked on the heating surface of boiler in the 
form of scale. 

Ones. Is a thick layer of scale in a boiler 
dangerous? 

Ans. Yes. Many boilers are ruined by the scale 
accumulating in sufficient quantities to burn or bag 
the fire plates. 

Ones. How does scale affect a boiler when 
not enough is present to be dangerous? 

Ans. It makes a boiler steam hard; scale, being 
a poor conductor of heat, will not transmit heat as 
readily as iron. 

Ques. Of what nature is scale? 

Ans. Scale in boilers may be of hard, rock like 
nature; or of soft, greasy, or powdery nature, accord- 
ing to its chemical and mechanical composition or 
formation. 

Ques. How does the scale get into the boiler 
water? 

Ans. The scale, or the ingredients that form the 
scale, get into the boiler by the feed water. 

Ques. How does the feed water receive the 
scale ingredients? 

Ans. The feed water for jet condensing plants is 
obtained from a different source from that of surface 



88 AUDELS ANSWERS ON 

condensing plants, therefore the scale formation is of 
a different nature for these two classes. 



Ones. From what does scale formation orig- 
inate in jet condesning plants? 

Ans. Scale formation in boilers of jet condensing 
plants results from salts, which were contained in 
the hard feed water, as obtained from the hot well, 
when drawn in by the vacuum of the condenser. 

Ques. What salts are most frequently found 
in the scale of the boiler? 

Ans. The salts found in the scale of boilers and 
deposited from the hard, fresh feed water are gen- 
erally various combinations of lime or magnesia. 

Ones. From what does scale formation orig- 
inate in surface condensing plants? 

Ans. Scale formation in boilers or surface con- 
densing plants results mainly from the sea water 
that enters the boiler, as feed make up, or through 
leakage of the condenser. Some of the salts are from 
sea water, at boiling, thrown down upon the heating 
surfaces, where they adhere very firmly. Cylinder oil 
produces scale, it being carried by the feed water into 
the boiler. 



PRACTICAL ENGINEERING 89 

Ones. How can the accumulation of scale in 
a boiler be reduced? 

Ans. By providing boiler with a surface blow off, 
as well as bottom blow off, and using both every day. 

ANALYSIS OF AVERAGE BOILER SCALE 

Parts per 100 parts 
of deposit. 

Silica . . . ' . .042 parts. 

Oxides of iron and aluminum .... .044 

Carbonate of lime 30.780 

Carbonate of magnesia 51.733 

Sulphate of soda . Trace 

Chloride of sodium Trace 

Carbonate of soda . . ... . . . 9.341 

Organic matter 8.060 



Total solids 100. parts. 

Ques. What other means are taken to keep 
a boiler free from scale? 

Ans. Chemicals to dissolve or neutralize the im- 
purities contained in the water are extensively used 
to prevent the formation of scale. 

Ques. Name some alkalis that are good to 
use in boilers in many localities for the pre- 
vention of scale? 

Ans. Sal soda, or soda ash. It may be put into 
boiler dry when it is opened up for cleaning, or it 



90 AUDELS ANSWERS ON 

may be dissolved and fed into boiler by pump ; being 
an alkali, it will not injure pump, pipes or the boiler. 
About 10 pounds of soda ash weekly will keep an 
ordinary sized boiler clean in New York City. 

Ques. Is kerosene sometimes used in boilers 
to prevent scale forming? 

Ans. Yes; although some engineers claim it will 
injure boiler if used a long time. When used, kero- 
sene is best fed into boiler through a sight feed 
lubricator, and it may be regulated to feed any 
desired quantity; the lubricator is piped up exactly 
as we would attach a lubricator to an engine. 

Ones. How are boilers tested? 

Ans. The boiler inspectors use the hydrostatic 
test. 

Ques. How is a hydrostatic test applied? 

Ans. By closing all pipe openings in boiler and 
filling boiler with water to safety valve; the safety 
valve is now blocked and enough more water is 
pumped into boiler until the steam gauge registers 
the desired amount of pressure. Boilers so tested 
are allowed to carry two-thirds the test pressure. 

Ques. How would you prepare for a test? 

Ans. I would clean the boiler thoroughly inside 
and outside, remove all ashes from ash pit and brush 
or blow out the tubes; the grate bars should be 
removed if boilers be internally fired, and safety 



PRACTICAL ENGINEERING 91 

valve and all stop valves should be made tight. The 
boiler may now be filled with water to safety valve, 
and we are now ready for the inspector to apply the 
pressure, which is done by connecting a force pump 
to some outlet in feed pipe and forcing water into 
boiler until the pressure is 50 per cent, in excess of 
the working pressure. All parts of the boiler are now 
carefully examined for leaks, and if none appear 
and the boiler be all right in other respects, a certifi- 
cate allowing the boiler to be put in service will be 
granted by the inspector. 

Ones. What else do boiler inspectors exam- 
ine? 

Ans. The safety valve and steam gauge. After 
applying pressure they see that the safety valve and 
gauge agree. 

Ones. If, in inspecting a boiler, you found 
one or more defective braces, what course would 
you follow? 

Ans. I would repair same, or have same repaired, 
before putting boiler in service again. 

Ques. If a boiler was to be put out of service 
for a year or more, how would you lay boiler up ? 

Ans. Clean the boiler thoroughly inside and out- 
side. By putting about 10 pounds of rock lime in a 
pan inside of boiler and closing all hand holes and 
pipe holes, boiler will remain perfectly dry for a 



92 AUDELS ANSWERS ON 

very long period ; the outside of boiler should be kept 
dry, damper should remain open, furnace doors 
closed and ash pit doors should remain open so that 
a draught of air is constantly passing through boiler. 
If the boiler is to be out of service only a short time, 
a good plan is to fill boiler entirely full of water and 
close all openings tight. 

Ques. Should the exposed parts of a boiler 
be covered? 

Ans. Yes; all exposed parts of a boiler should be 
carefully covered with asbestos or other good insu- 
lators. 



PRACTICAL ENGINEERING 93 



ENGINEERS' LAW 



Law under which all engineers are licensed in 
the City of New York. 

LAWS OF NEW YORK.— By Authority. 

Chap. 635. 

AN ACT to amend chapter four hundred and ten of the laws of 
eighteen hundred and eighty-two, entitled "An act to 
consolidate into one act and to declare the special and local 
laws affecting public interests in the City of New York," 
relative to engineers. 

Accepted by the city. 

Became a law May 22, 1897, with the approval of the Governor, 

Passed, three-fifths being present. 

The People of the State of New York, represented in Senate and 
Assembly, do enact as follows: 

Section 1. Section three hundred and twelve of chapter four 
hundred and ten of the laws of eighteen hundred and eighty-two 
is hereby amenced so as to read as follows: 

Section 312. The board of police shall preserve in proper form 



94 AUDELS ANSWERS ON 

a correct record of all Inspections of steam boilers made under 
its direction, and of the amount of steam or pressure allowed in 
each case, and in cases where any steam boiler or the apparatus 
or appliances connected therewith shall be deemed by the board 
after inspection, to be insecure or dangerous, the board shall 
prescribe such changes and alterations as may render such boilers, 
apparatus and appliances secure and devoid of danger. And in 
the meantime, and until such changes and alterations are made, 
and such appliances attached, such boiler, apparatus, and ap- 
pliances may be taken under the control of the board of police, 
and all persons prevented from using the same, and in cases 
deemed necessary, the appliances, apparatus, or attachments 
for the limitation of pressure may be taken under the control 
of the said board of police. And no owner, or agent of such 
owner, or lessee of any steam boiler to generate steam, shall 
employ any person as engineer or to operate such boiler unless 
such person shall first obtain a certificate as to qualification 
therefor from a board of practical engineers detailed as such by 
the police department, such certificate to be countersigned by 
the officer in command of the sanitary company of the police 
department of the city of New York. In order to be qualified 
to be examined for and to receive such certificate of qualification 
as an engineer, a person must comply, to the satisfaction of said 
board, with the following requirements: 

i . He must be a citizen of the United States and over twenty- 
one years of age. 

2. He must, on his first application for examination, fill out, 
in his own handwriting, a blank application to be prepared and 
supplied by the said board of examiners, and which shall contain 
the name, age, and place of residence of the applicant, the place 
or places where employed and the nature of his employment 
for five years prior to the date of his application, and a statement 



PRACTICAL ENGINEERING 95 

that he is a citizen of the United States. The application shall 
be verified by him, and shall, after the verification, contain a 
certificate signed by three engineers, employed in New York 
City, and registered on the books of said board of examiners as 
engineers working at their trade, certifying that the statements 
contained in such application are true. Such application shall 
be filed with said board. 

3. The following persons, who have first complied with the 
provisions of subdivisions one and two of this section, and no 
other persons, may make application to be examined for a license 
to act as engineer. 

a. Any person who has been employed as a fireman, as an 
oiler, or as a general assistant under the instructions of a licensed 
engineer in any building or buildings in the city of New York, 
for a period of not less than five years. 

b. Any person who has served as a fireman, oiler or general 
assistant to the engineer on any steamship, steamboat, or any 
locomotive engineer for the period of five years and shall have 
been employed for two years under a licensed engineer in a 
building in the city of New York. 

c. Any person who has learned the trade of machinist, or 
boilermaker or steamfitter and worked at such trade for three 
years exclusive of time served as apprentice, or while learning 
such trade, and also any person who has graduated as a mechanical 
engineer from a duly established school of technology, after such 
person has had two years experience in the engineering department 
in any building or buildings in charge of a licensed engineer, 
in the city of New York. 

d. Any person who holds a certificate as engineer issued to him 



96 AUDELS ANSWERS ON 

by any duly qualified board of examining engineers existing pur- 
suant to law in any state or territory of the United States and 
who shall file with his application a copy of such certificate and 
an affidavit that he is the identical person to whom said certificate 
was issued. If the board of examiners of engineers shall determine 
that the applicant has complied with the requirements of this 
section he shall be examined as to his qualifications to take charge 
of and operate steam boilers and steam engines in the city of 
New York, and if found qualified said board shall issue to him 
a certificate of the third class. After the applicant has worked 
for a period of two years under his certificate of the third class, 
he may be again examined by said board for a certificate of the 
second class, and if found worthy the said board may issue to him 
such certificate of the second class, and after he has worked for 
a period of one year under said certificate of the second class he 
may be examined for a certificate of the first class, and when it 
shall be made to appear to the satisfaction of said board of exam- 
iners that the applicant for either of said grades lacks mechanical 
skill, is a person of bad habits or is addicted to the use of intox- 
icating beverages he shall not be entitled to receive such grade 
of license and shall not be re-examined for the same until the 
expiration of one year. Every owner or lessee, or the agent 
of the owner or lessee, of any steam boiler, steam generator, or 
steam engine aforesaid, an every person acting for such owner or 
agent is hereby forbidden to delegate or transfer to any person 
or persons other than the licensed engineer the responsibility 
and liability of keeping and maintaining in good order and con- 
dition any such steam boiler, steam generator or steam engine, 
nor shall any such owner, lessee or agent enter into a contract 
for the operation or management of a steam boiler, steam gen- 
erator or steam engine, whereby said owner, lessee or agent shall 
be relieved of the responsibility or liability for injury which 
may be caused to person or property by such steam boiler, steam 
generator or steam engine. Every engineer holding a certificate 
of qualification from said board of examiners shall be responsible 



PRACTICAL ENGINEERING 97 

to the owner, lessee or agent employing him for the good care, 
repair, good order and management of the steam boiler, steam 
generator or steam engine in charge of or run or operated by 
such engineer. 

Sec. 2. This act shall take effect immediately. 



AUDELS ANSWERS ON 



FIREMEN'S LAW 



To provide for the licensing of firemen operating steam 
stationary boiler or boilers in the City of New York. 

Accepted by the City. 

Became a law May 13, 1901, with the approval of the Governor. 

Passed, three-fifths being present. 

The people of the State of New York, represented in Senate and 
Assembly, do enact as follows : 

Section 1. It shall be unlawful for any fireman or firemen to 
operate steam stationary boilers in the City of New York, unless 
the fireman or firemen to operating such boiler or boilers are 
duly licensed as hereinafter provided. Such fireman or firemen 
to be under the supervision and direction of a duly licensed engi- 
neer or engineers. 

Section 2. Should any boiler or boilers be found at any time 
operated by any person who is not a duly licensed fireman or 
engineer as provided by this act, the owner or lessee thereof 
shall be notified, and if after one week from such notification 
the same boiler or boilers is again found to be operated by a 
person or persons not duly licensed under this act, it shall be 
deemed prima facie evidence of a violation of this act. 

Section 3. Any person desiring to act as a fireman shall make 
application for a license to so act, to the steam boiler bureau of 
the police department as now exists for licensing engineers, who 



PRACTICAL ENGINEERING 99 

shall furnish to each applicant blank forms of application, which 
application when filled out shall be signed by a licensed engineer 
engaged in working as an engineer in the City of New York, who 
shall therein certify that the applicant is of good character, and 
has been employed as oiler, coal passer or general assistant under 
the instructions of a licensed engineer on a building or buildings 
in the City of New York, or on any steamboat, steamship or loco- 
motive for a period of not less than two years. The applicant 
shall be given a practical examination by the board of examiners 
detailed as such by the police commission and if found competent 
as to his ability to operate a steam boiler or steam boilers as 
specified in Section 1 of this Act, shall receive within six days 
after such examination a license as provided by this Act. Such 
license may be revoked or suspended at any time by the police 
commissioner upon the proof of deficiency. Every license issued 
under this Act shall continue in force for one year from the date 
of issue unless sooner revoked as above provided. Every license 
issued under this act unless revoked as herein provided, shall 
at the end of one year from date of issue thereof, be renewed by 
the board of examiners upon application and without further 
examination. Every application for renewal of license must be 
made within thirty days of the expiration of such license. 

With every license granted under this Act there shall be 
issued to every person obtaining such license a certificate, 
certified by the officers in charge of the boiler inspection bureau. 
Such certificate shall be placed in the boiler room of the plant 
operated by the holder of such license, so as to be easily read. 

Section 4. No person shall be eligible to procure a license 
under this Act unless the said person be a citizen of the United 

States. 

Section 5. All persons operating boilers in use upon loco- 
motives or in government buildings, and those used for heating 
purposes carrying a pressure not exceeding ten pounds to the 
square inch, shall be exempt from the provisions of this Act. 



100 



AUDELS ANSWERS ON 



Such license will not permit any person, other than a duly- 
licensed engineer to take charge of any boiler or boilers in the 
City of New York. 

Section 6. This act shall take effect immediately. 



PRACTICAL ENGINEERING 101 



STEAM ENGINES 



Ques. Name the different classes of engine. 

Ans. Engines may be divided into three great 
classes : Stationary, marine and locomotive. 

Ones. What are the principal types of 
stationary engine? 

Ans. Stationary engines may be divided into 
three classes: Common slide valve, automatic and 
Corliss engines. 

Ques. How is a common slide valve engine 
constructed ? 

Ans. The common slide valve engine is the 
simplest form of engine, having one slide valve 
moved by an eccentric and rod. 

Ones. What is an automatic engine? 

Ans. In this type of engine the speed is kept 
constant by a governor mounted on crank shaft and 
usually placed in one of the band wheels. Most 
automatic engines have double ported balanced slide 
valves, and are usually run at a high speed. 



102 AUDELS ANSWERS ON 

Ques. What is a Corliss engine? 

Ans. A steam engine fitted with Corliss valves. 
These are four in number for each cylinder, 
a separate steam and exhaust valve being provided 
at each end. The valves are shaped as a sector of a 
cylinder and vibrate within a cylindrical seat over 
ports in line therewith. The admission valves are not 
in positive connecticn with the valve gear, but are 
tripped or disengaged at a point in the stroke deter- 
mined by the governor or by hand, the closing being 




Fig. 47. — Plain horizontal slide valve engine; view showing parts. 

effected by the action of the dash pot thus giving 
a quick cut off, variable according to the load. The 
Corliss engine has a very small percentage of clear- 
ance. 

Ques. What may be said in favor of the slide- 
valve engine? 

Ans. It is cheap, simple and easily kept in re- 
pair, and little skill is necessary to operate one 



PRACTICAL ENGINEERING 



103 



successfully. It is used in small plants where the 
economical production of power is not of first im- 
portance. 




Fig. 48. — A throttling governor. In operation, as the engine speeds up, the 
centrifugal force acting on the balls causes them to swing outward, which in 
turn, through suitable connections, closes the steam valve, resulting in 
maintaining a nearly constant speed at all loads. 



Ques. How is the speed regulated on a slide 
valve engine? 

Ans. By a throttling ^governor, which is placed on 
valve chest, and driven by a small belt from crank 
shaft. This governor controls the amount of steam ad- 
mitted to engine and keeps the speed fairly constant. 



104 



AUDELS ANSWERS ON 



Ques. Are automatic engines in extensive 
use? 

Ans. Yes; this type of engine is very much used, 
principally for electric lighting, and for power in 
mills, factories, hotels, etc. It occupies little space, 




Pig. 49. — The Sturtevant automatic high speed engine. The term high speed 
is here used in the sense of "quick revolution" rather than high piston 
speed. A shaft governor is used with this type of engine. It operates by 
shifting the eccentric so as to vary the throw; this changes the travel of the 
valve, thus altering the cut off to suit the load. 



has a very sensitive governor, is fairly economical in 
the use of steam, but requires much attention to be 
kept in repair. Automatic engines are short stroke 
engines and are operated at a high rotative speed. 



PRACTICAL ENGINEERING 105 

Ques. Of what material are the principal 
wearing parts of an engine made? 

Ans. The crosshead pin is usually made of tool 
steel ground true, the crosshead shoes are made of 
brass on small engines and are babbitted on large 
engines. -The crosshead boxes are usually made of 
phosphor bronze or brass. The crank pin is made of 
tool steel ground true, and turns in brass boxes lined 
with babbitt metal. The crank shaft is made of 
machine steel and runs in cast iron boxes lined with 
babbitt metal; the eccentric is usually made of cast 
iron throughout. 

Ones. What is a crosshead? 

Ans. The crosshead is that part of an engine 
which fits loosely in the guides, and to which the 
piston rod and connecting rod are attached. 

Ques. What is the connecting rod? 

Ans. The connecting rod forms the link between 
crank and crosshead of an engine; the crosshead, 
connecting rod and crank convert a straight back 
and forward motion into a rotary motion. 

Ones. What is the nature of the strain on the 
piston rod? 

Ans. It is alternately tensile and compression. 

Ones. What is the nature of the strain on 
connecting rod? 

Ans. Tensile, compression and bending. 



106 AUDELS ANSWERS ON 

Ques. Why is an engine crank shaft usually 
provided with only two bearings? 

Ans. Because two bearings are much more easily 
kept in line than a greater number. 

Ques. What is the nature of the strain on 
crank shaft? 

Ans. The strain on shafts is torsional (twisting), 
and for that reason they must be made much stronger 
than piston and connecting rods. 

Ques. Why are the crank pin boxes and 
crank shaft bearings lined with babbitt metal? 

Ans. So that the boxes will wear faster than the 
crank pin and shaft. When the boxes are worn large 
they may be re-babbitted. 

Ques. What is a fly wheel on an engine for? 

Ans. To smooth out any slight irregularity of 
speed; fly wheels on some engines are made very 
heavy, with most of the weight placed in the rim 
of wheel, where it will do the most good; on other 
engines the fly wheel is also used as a band or driv- 
ing wheel. 



PRACTICAL ENGINEERING 



107 



THE VALVE AND 
VALVE GEAR 



Ques. Describe a slide valve. 

Ans. A slide valve is a cup shaped piece of metal 
arranged to slide over and alternately cover and 
uncover the openings or ports through which steam 




Fig. 50. — A plain unbalanced slide valve. The parts are: M, valve; S. seat; 
O, steam edges; I, exhaust edges; CD, steam ports; P, steam passages; 
IT, exhaust port; DP, bridge; F, cavity; G, exhaust cavity; OC, outside 
lap: DI, inside lap. 



is distributed to the cylinder; called also, D valve 
and D slide. It is situated in the steam chest, and is 
moved by the valve gear. 



108 AUDELS ANSWERS ON 

Ones. What are the good points of the slide 
valve gear? 

Ans. Its simplicity, and the little attention re- 
quired to keep it in order. 

Ones. What are the principal objections to 
the slide valve? 

Ans. As the full pressure of the steam presses valve 
to its seat, much power is necessary to move valve, 
and if not liberally lubricated both valve and seat will 
wear rapidly; with this style of valve, cut off cannot 
take place earlier than J^ stroke. 

Ones. What is a balanced slide valve? 

Ans. A balanced valve has its back ground true 
and slides between valve seat and a pressure plate; 
this type of valve is used on automatic engines. 

Ones. What is lap? 

Ans. That amount of the valve that is more than 
necessary to cover the ports; in other words, the 
amount the valve laps over the ports, when the valve 
is in its central or neutral position. 

Ones. Name two kinds of lap. 

Ans. Inside lap and outside lap. 

Ques. What is outside lap? 

Ans. The distance from the steam edge of the 
steam port to the steam edge of the valve when the 
valve is in its neutral or central position. 



PRACTICAL ENGINEERING 109 

Ones. What is inside lap? 

Ans. The distance from the exhaust edge of the 
steam port to the exhaust edge of the valve when the 
valve is in its neutral position. 

Ques. What is the object of outside lap? 

Ans. To close the steam port before the piston 
reaches the end of stroke. When the valve is closed 
(when cut off begins) the steam in cylinder must ex- 
pand to finish stroke. 

Ques. What regulates the cut off? 

Ans. The amount of lap; the more lap the earlier 
the cut off. 

Ques. At what part of stroke does the cut 
off take place in slide valve engines? 

Ans. At from ^ to % stroke. 

Ques. What is the object of inside lap? 

Ans. To secure later release of the steam and more 
compression. 

Ques. When the exhaust edge of valve closes 
the exhaust port what takes place? 

Ans. Compression; that is, the remaining ex- 
haust is compressed, and assists in bringing the 
piston to a stop. 



110 AUDELS ANSWERS ON 

Ques. What is meant by lead? 

Ans. Lead is the amount of opening of valve as 
the engine begins the stroke; engineers give their en- 
gines lead so that the clearance space in cylinder is 
full of steam at boiler pressure when the engine be- 
gins its stroke. 

Ques. Should more lead be given an engine 
on the crank end than head end? 

Ans. Many engineers give the valve a trifle more 
lead on the crank end because the piston is somewhat 
smaller in area, due to the piston rod being attached 
to piston, also any lost motion in the eccentric rods 
tends to decrease the lead on crank end and increase 
the lead on head end. 

Ques. How much lead would you give a 
small engine, say about 10 horse power? 

Ans. About -^ inch, or a little less. 

Ques. What is negative lead? 

Ans. The amount by which the steam edge of the 
valve overlaps the steam edge of the port when the 
engine is on the dead center. 

Used sometimes on locomotives having link motion to prevent 
excessive positive lead when cutting off short. 

Ques. If an engine valve had neither lap nor 
lead, how much in advance of the crank would 
you place the eccentric? 

Ans. When an engine has neither lead nor lap 



PRACTICAL ENGINEERING 111 

the eccentric would be placed exactly 90 degrees or 
34 turn in advance of the crank, that is, the angular 
advance would be zero. 

Ques. What is the angular advance of the 
eccentric ? 

Ans. The angular advance is the amount that 
the eccentric is more than 90 degrees in advance 
of the crank. The greater the lap the greater will 
be the angular advance. 

Ones. In a slide valve engine how much is 
the eccentric placed in advance of the crank? 

Ans. The eccentric is placed in advance about 
115 degrees more or less. No rule can be given that 
will apply in general; in all engines the eccentric 
is placed enough more than 90 degrees in advance 
of the crank to give sufficient lead. 

Ques. What is the travel of a slide valve? 

Ans. The extent of the movement of the valve in 
either direction; for full gear, it is equal to twice the 
outside lap plus twice the port opening. 

Ques. What part of the cylinder volume is 
clearance space. 

Ans. The clearance space is the space between 
the piston and cylinder head when engine is on 
dead center, plus the volume of the steam passage 



112 AUDELS ANSWERS ON 

leading from valve to cylinder; it amounts to from 
2 to 10 per cent, of the total cylinder volume. 

Ques. Is the steam that fills the clearances 
altogether wasted? 

Ans. No; when cut off takes place it expands and 
does some work. 

Ques. Should this clearance space be kept 
as small as possible? 

Ans. Yes; as the steam that fills the clearance 
performs little work, it should be kept as small as 
possible. 

Ones. How do we set the valve on a com- 
mon slide valve engine? 

Ans. Turn the eccentric on the shaft so that the 
high part of the eccentric, will be about one-quarter 
of a revolution in advance of the crank (by 
advance is meant in the direction the engine is to 
run) when the engine is on dead center. Now 
square the valve over ports by adjusting the locknuts 
that hold it on valve rod. This done, turn the ec- 
centric on shaft until valve has the proper amount 
of lead (if engine run "over" eccentric will have to 
be turned in the direction of rotation; if engine 
run ' 'under" the eccentric must be moved back). 
Make the eccentric fast on shaft when the lead is 
right, and turn the engine on the opposite dead 



PRACTICAL ENGINEERING 



113 



center, and if the lead be the same as on the other 
end the valve is properly set. If the lead be unequal 
it must be equalized by adjusting the valve stem. 

By placing the engine on the dead center and turn- 
ing the eccentric in the reverse direction of rotation 




Fig. 51. — Section of cylinder showing the construction of a piston valve. This 
type of valve is cylindrical in form, the seat consisting of a cylindrical ring 
containing the ports. As shown in the figures, the valve is arranged for 
inside admission. 



until the valve again comes into the lead position; 
this may be done without taking off the steam chest 
cover, by means of a scriber and a reference mark on 
the valve stem. 



114 AUDELS ANSWERS ON 

Ques. How is the cut off arranged in an auto- 
matic engine? 

Ans. In the automatic engine the cut off is ad- 
justable and is effected by the shaft governor varying 
the throw of eccentric, which varies the valve 
travel and cut off to suit the boiler pressure and load 
of engine. 

Ques. How do we set the valve, on an auto- 
matic engine fitted with a double ported bal- 
anced valve and pressure plate? 

Ans. To set the valve the governor weights are 
propped out sufficiently to cause the valve to cut off 
at about }4 stroke, and the locknuts on valve rod are 
adjusted to give the same amount of lead on both 
ends of cylinder when the engine is on dead centers. 



PRACTICAL ENGINEERING 115 



THE CORLISS ENGINE 



Ones. What may be said of the Corliss en- 
gine? 

Ans. This engine is complicated, but very econom- 
ical; it occupies much more space than an automatic 
engine of the same power, is high at first cost, and 
requires a skillful engineer. 

Ques. How much lap have the Corliss engine 
valves ? 

Ans. The amount of lap depends upon the size of 
engine and is always small in all Corliss engines, 
because, unlike the slide valve engine cut off, does 
not depend upon the amount of lap when engine is 
up to speed. 

Ones. Is the clearance smaller in Corliss 
engines than in most of the other types? 

Ans. Yes; the clearance is always small in Corliss 
4 engines ; in large engines it is usually about 3 per 
cent, of the total cylinder volume. 



AUDELS ANSWERS ON 




PRACTICAL ENGINEERING 117 

Ques. Why do we require so little compres- 
sion in the Corliss engine? 

Ans. Because its rotative speed is low. 



Ques. How do we set the valves on a Corliss 
engine? 

Ans. The following will be found sufficiently gen- 
eral to apply to all Corliss engines: 



TO SET THE CORLISS VALVES 

Remove the back valve .chest bonnets and upon 
the bore of the seats will be found a mark indicating 
the closing edge of port. On the end of valve is a 
mark representing the closing edge of valve; note 
that in the case of the exhaust valve, the valve controls 
the port leading into the exhaust chest and not the 
opening from the cylinder downward, the outer edge 
of port in exhaust valve is the closing edge and the 
outer edges of the steam valves are the closing edges. 

The wrist plate should now be looked over. On 
the back of wrist plate will be found a center line, 
and a line will also be found on the hub of stand 
supporting wrist plate, also on either side of central 
mark will be lines which show the vibration of wrist 
plate, and when the line on wrist plate coincides with 



118 



AUDELS ANSWERS ON 



either of these lines it will be in its extreme position. 
The wrist plate should be located exactly central 
between the four valves, and is so placed in the shop 
in building the engine, and all adjustments are made 




Fig. 53. — One end of Corliss cylinder showing operation. Steam enters the 
cylinder casing by the opening for the steam pipe flange 7, and flows around 
the cylinder barrel in the annular passage 5. It gains admission past the 
steam valve 1, through the admission port 3, into the bore of the cylinder 
9. After peforming its work upon the piston the steam passes through the 
exhaust port 4 and exhaust valve 2, into the exhaust passage 6, finally 
escaping to the atmosphere or condenser through the exhaust outlet 8; the 
cylinder cover 10 is not jacketed in this instance. 



and valves properly set, but in taking apart for ad- 
justment, it may be possible that the adjustments 
may be disturbed, and need careful going over be- 
fore attempting to start the engine for the first 
time. 



PRACTICAL ENGINEERING 



119 



To test the marks on wrist plate and stand, con- 
nect the eccentric rod and hook rod, then rotate the 
eccentric on the shaft the full throw each way, and 
observe if the mark on the wrist plate at full throw 
agree with marks on stand; if not, to set the valves 




Fig. 54. — Corliss valves: 1, steam valve; 2, exhaust valve. The recesses a, 
cut across the face of the circular end of the valves, are to receive a T shaped 
head of -the valve stems, which transfers the rotary motion of the latter to 
the valves, and still allows the valves to be withdrawn from their respective 
chambers by removing the covers on the front side of the engine. It also 
enables the valves to leave their seats, if forced by water or over pressure, 
and to follow up near without bending the valve stem. 



adjust the nuts on eccentric rod (or stub end, as the 
rod may be constructed), and by lengthening or 
shortening (as required) until the marks agree on 
both extremes of vibration of wrist plate. Place the 
wrist plate in a vertical position at the central mark, 
turn the valves until the " steam valves " show by the 



120 



AUDELS ANSWERS ON 



marks on valve and seat that the closing edges lap as 
per table below, and the marks on exhaust valve and 
seat show opening as per table below: 



Cyl. 10 to 14 ins. diam., 
Cyl. 16 to 20 ins. diam., 
Cyl. 22 to 30 ins. diam., 



X -m - steam lap, X6~in. exh. open. 
3/g-in. steam lap, jV" m - exh. open. 
3^ in. steam lap, 3^-in. exh. open. 




Fig. 55. — Reynolds-Corliss engine; view showing valve gear. 



The valves at both ends of cylinder should be alike, 
and can be adjusted by means of the right and left 
hand screws in connecting links, so that the lap and 
opening stand exactly the same in both ends of the 
cylinder. 

With the valves and connections properly adjusted, 
drop the hook on wrist plate pin, place the engine on 



PRACTICAL ENGINEERING 121 

either center (if engine is to run over, it will be more 
convenient to place it on inner center), turn the 
eccentric upon the shaft in the same direction in 
which the shaft is to run, a little more than at right 
angles ahead of the crank or until the steam valve on 
the same end as the piston has the proper amount of 
lead; in this position secure the eccentric on shaft 
(see in all cases that the steam valves are hooked up 
or engaged by the cut off mechanism), then turn the 
engine on the opposite center and see if the steam 
valve on that end has the same opening; if not, make 
the adjustment by shortening or lengthening, as may 
be required, the connection between the valve and 
wrist plate. 

TO ADJUST THE CUT OFF 

See that the governor and connections are properly 
put together, block the governor up half-way of its 
rise when resting on safety collar, then fasten cam 
rod lever so that it stands about right angles to a 
line drawn midway between the cam rods, then 
adjust the cam rods so that the cam lever stands 
vertical, the governor and connections now occupy 
the proper relative positions. Now lower the gov- 
ernor on safety collar, and see that the cut off mechan- 
ism does not unhook, but allows steam to be taken 
full stroke ; now throw the safety collar around so that 
governor can drop the extra travel, and see that the 



122 



AUDELS ANSWERS ON 




<u o 

fi 



PRACTICAL ENGINEERING 



123 



catch block is disengaged so that valve will not open. 
This safety catch is to prevent engine running 
away in case governor belt breaks, and should be 
thrown back when engine is in motion, but should 
be put in place before stopping engine. 




Fig. 57. — The Murray-Corliss releasing gear. 

To equalize the cut off at each end of stroke, place 
the engine at, say, 34 stroke, which can be done by 
measuring upon the slides from each end and turning 
the engine until crosshead is in line with the mark; 
then raise the governor until the cut off on the end 
taking steam, trips or unhooks; now block the governor 



124 AUDELS ANSWERS ON 

in this position and try the cut off on the other stroke, 
same distance from end, and adjust length of cam 
rods so that cut off unhooks at same point of stroke. 
The dash pot rod should be adjusted so that the 
latch is sure to hook under the latch stud on steam 
valve stem arm when the plunger is at bottom of 
dash pot. 

GOVERNOR DASH POT 

The dash pot attached to governor is used to pre- 
vent over sensitiveness and too sudden response to 
trivial changes. Do not allow it to become gummed 
with oil, but keep it clean, and use only coal or kero- 
sene oil in the pot. Adjust the screw in piston 
which acts as a valve to allow the oil to pass from 
one side of piston to the other to give freedom of 
motion. 

See that all parts of the governor move freely; a 
little kerosene oil run through all its parts occasionally 
will prevent gumming. 



PRACTICAL ENGINEERING 125 

ARITHMETIC 

OF THE 

STEAM ENGINE 



Ones. How do we find the piston speed of 
any engine? 

Ans. By multiplying twice the number of revolu- 
tions per minute by the stroke of engine in inches, 
and dividing the product by 12, to reduce to feet. 

Ques. What are the usual piston speeds for 
stationary work? 

Ans. From 350 to 800 feet per minute. 

Ques. How can we find the length of stroke 
of any engine without disturbing cylinder? 

Ans. By finding the distance between center of 
shaft and center of crank and multiplying by 2. 

Ques. How do we find the area of piston? 

Ans. By squaring the diameter and multiplying 
the product by .7854. 

Ques. What is the mean effective pressure? 

Ans. The mean effective pressure is the average 
pressure exerted on piston throughout one stroke. 

To find the mean effective pressure exactly we must use an 
indicator; if no indicator be at hand we estimate it roughly from 



126 AUDELS ANSWERS ON 

the boiler pressure by multiplying the latter by from 
.40 to .70, according to how early cut off takes place, or more 
accurately by the use of hyperbolic logarithms. 

Ques. What is a horse power? 

Ans. 33,000 foot pounds of work done in one 
minute is a horse-power; in other words, a horse- 
power is equivalent to the work of raising a weight 
of 33,000 pounds one foot in one minute. 

Ques. How do we find the horse power that 
a certain engine will develop? 

Ans. Multiply the mean effective pressure by 
the area of piston in square inches and multiply the 
product by the length of stroke in feet, and by the 
number of strokes per minute (twice the number 
of revolutions); divide this last product by 33,000 
and the answer will be the horse power. The formula 
for finding the horse power of a double acting engine 
is usually written: 

2 PLAN 
33000 

P = Mean effective pressure per square inch ; 

L = Length of stroke in feet ; 

A = Area of piston in square inches; 

N = Number of revolutions per minute. 

The following example shows method of computing 
the power of a 16 x 42 engine, with 84 revolutions 



PRACTICAL ENGINEERING 127 

per minute and mean effective pressure 40 pounds; 
cylinder diameter 16 ins.; stroke 42 ins.; revolutions 
84; mean effective pressure 40 lbs. 



1st Step 

16 




16 
96 
16 


2nd Step 

201 . 06 piston area 


256 


40 mean effective pressure 


.7854 
1024 


8042 . 40 lbs., total pressure 
upon the piston 


1280 




2048 




1792 





201 . 0624 piston area in sq. ins. 

4th Step 

3rd Step 8042. 4 lbs., total pressure 

42 ins = 3 . 5 stroke 588 ft. piston speed 

3.5 X 2 = 7 ft. per rev. 643392 

84 rev. per min. 643392 

7 ft. per rev. 402120 



588 ft, piston speed 4728931.2 foot pounds 

per minute 

5th Step 

4728931.2 4- 33000 = 143.3 horsepower. 



128 



AUDELS ANSWERS ON 




PRACTICAL ENGINEERING 129 

Ques. What is an indicator card? 

Ans. An indicator card or diagram is the dia- 
gram penciled, by the indicator, on a sheet of paper 
from which we figure horse power, pressure, vol- 
ume, etc. 



jUgj 



Fig. 59. — Ideal indicator card, with pre-release and compression; the card repre- 
sents ideal action; however this does not occur in practice. It takes time 
for the valve to open for admission and to close for cut off, hence the corners 
of the diagram taken from an angle will not be so sharp as in the figure ; the 
expansion line is usually distorted on account of the cylinder condensation 
and re-evaporation. The curve at the toe of the diagram shows the effect 
of the gradual opening of the valve at pre-release. 

Ones. How do we find the area of an indica- 
tor card and the mean effective pressure? 

Ans. We can find the area directly and accurately 
by the planimeter, which is an instrument for finding 
the area of bodies of irregular shape ; if no planimeter 
be at hand, a method much used and fairly accurate 
is to find the average height of the diagram by draw- 
ing ten lines or ordinates through the diagram from 



130 AUDELS ANSWERS ON 

top to bottom, at equal distances apart; by addir 
the lengths of these lines together and dividing tl 
sum by 10, the average height of diagram is foun 
and this multiplied by the length of diagram and t 
the scale of spring will be the mean effective pressur 



Ques. How do we find the mean effects 
pressure from an indicator diagram? 

Ans. By multiplying the area of card by the sea 
of spring. 

Ques. What data should be noted in takir 
an indicator card? 

Ans. The data that should be recorded on the ca\ 
are: 

1. Diameter and end of cylinder to which tl 
card belongs; 

2. The scale of the spring that has been used; 

3. The number of revolutions per minute; 

4. The pressure from the steam and receiver gaug 
and the vacuum; 

5. Degree of opening of throttle; 

6. Time, date, cut off of cylinder and other detail 
as desired. 



PRACTICAL ENGINEERING 



131 



Ques. What is an indicator? 

Ans. An instrument for finding the pressure 
within the cylinder at any part of the stroke; in 
fact, by the indicator we find exactly what is going 
on inside the cylinder. 




IIS ' ' 



Fig. 60. — The indicator. It consists of a small cylinder communicating by a 
cock with the cylinder of the engine, and fitted with a piston, to which a 
pencil is attached. The roller upon which a card is fastened, is oscillated 
forward and backward by a cord attached to the piston rod of the engine 
as the pencil rises by the steam pressure, and is brought back by a grad- 
uated spring when that pressure is reduced. This traces a closed figure upon 
the card, which represents the pressure at each point in the stroke of the 
engine. 

In all cases where it is possible and an indicator can be obtained, 
it should be applied to test the correctness of valve setting. 

The connection between the indicator and the steam cylinder 
of the engine must be as direct as possible, so that the same 



132 AUDELS ANSWERS ON 

pressure that is acting upon the piston in the engine may at the 
same instant act upon the piston in the indicator. 

Almost all modern engines are tapped for the indicator; but 
if no provision be made, the holes should be drilled into 
the counterbore of the cylinder, and tapped for a half inch pipe 
thread. 

Care should be taken that none of the drill chips drop into 
the engine cylinder, and that the holes thus drilled are not 
obstructed by the piston. 

When the connections are all up, allow the steam to blow 
through them freely some time before attaching the instrument, 
to remove any scale or dirt that is liable to become detached. 



PRACTICAL ENGINEERING 133 



LUBRICATORS 



Ques. What is a lubricator? 

Ans. A device to hold oil and supply it in regular 
amounts to a bearing or cylinder. 

The term lubricator is applied more especially to an oiling 
device intended for internal lubrication, that is for cylinder lubri- 
cation. A few examples of lubricator are shown in figs. 64, 65, 
66 and 67. 

Ques. Describe the different methods of feed 
for external lubrication. 

Ans. The supply is fed either by worsted syphons, 
by gauged drips, or by a needle, placed in the oil 
passage through the neck of the lubricator, and which 
induces feeding by capillary attraction and the shaking 
of the needle. 

Ques. What is a sight feed lubricator? 

Ans. One that passes the oil visibly, drop by drop, 
through a section of glass tube so that its rate of 
supply may be observed. The term is usually applied 
to those types designed for feeding oil into the engine 
cylinder, that is, those intended for internal lubrica- 
tion. 



134 AUDELS ANSWERS ON 

Ques. What is the principle of operation of 
a sight feed lubricator? 

Ans. The condensation of steam displaces oil from 
a vessel under pressure, the weight of the column of 
water plus the steam pressure forcing the drops of oil 
along pipes to the desired spot. 




Figs. 61 and 62. — Sentinel sight feed oil cup; fig. 61, lever down feed shut off; 
fig. 62, lever up, cup feeding. To adjust feed raise the lever and turn the 
milled thumb nut until the desired feed is obtained. When the lever is set 
at an angle of 45 degrees it raises the feed stem clear off its seat and cup 
flushes. 

Fig. 63. — Oiler for movable bearings. The feeding arrangement consists of a 
tube, screwed into the base of the cup and communicating with the oil hole 
in the shank. Secured to the top of this tube is a regulating valve, by means 
of which any quantity of oil can be fed through the tube. 



PRACTICAL ENGINEERING 



135 



Ques. Describe the construction and opera- 
tion of a sight feed lubricator. 

Ans. Figs. 64 and 65 show external and sectional 
views of a sight feed lubricator. The pipe P shown in 
sectional cut on the right, connects with a passage 




Figs. 64 and 65.— Detroit sight feed lubricator. The parts are Al, body of 
oil reservoir; A2, condenser; A3, filler plug; A4, water feed valve stem- 
A5, plug for inserting sight feed glass; A6, sight feed glass drain stemj 
A7, sight feed regulating valve stem; A8, drain valve; A9, globe valve in 
support arm; A10, plug for inserting gauge glass; H, sight feed glass; J, 
gauge glass; K, connection to steam pipe. 



136 AUDELS ANSWERS ON 

from condenser A-2, so that as soon as the water feed 
valve A-4 is opened, the water in the condenser will 
pass down the pipe P, to the bottom of the body of 
the lubricator, and being heavier than oil, will stay 
at the bottom, the oil floating above it. The pipe S, 
leads to the lower sight-feed arm from the upper part 
of the body of the lubricator. The body A-l is filled 
with oil. Steam from the main steam pipe passes in 
the connecting pipes above the lubricator, and con- 
denses, filling the condenser A-2 and part of the pipe 
above it with water. The steam also passes into the 
support arm and through the internal tube T into the 
sight feed glass, where it condenses, filling the glass 
with water. As soon as the valve A-4 is opened, the 
oil in the body of the lubricator is subjected to the 
pressure of the column of water extending through 
the pipe P, the condenser and part of the pipe above 
it, amounting to about 2 lbs. to the square inch, and 
in addition to the pressure of the steam above the 
water, amounting to say 100 lbs. to the square inch, 
or a total pressure of about 102 lbs. to the square inch. 
This we may call the positive pressure. Liquids com- 
municate pressure equally in all directions, so the oil 
in the body of the lubricator will press in every 
direction with a force of about 102 lbs. to the square 
inch. It will therefore press down through the tube 
S with this force of 102 lbs. to the square inch. Then, 
if the valve A-7 be opened, a force acting in the op- 
posite direction is encountered, which we may call the 



PRACTICAL ENGINEERING 



137 



back pressure. When the lubricator is connected as 
shown, this back pressure will consist of the column 
of water in the sight feed glass, and in addition, the 
steam pressure back of this column entering through 
the support arm, and amounting to 100 lbs. to the 
square inch. The positive steam pressure being just 





Fig. 66. — Plain cylinder lubricator without sight feed. 

Fig. 67.— Graphite sight feed lubricator. To operate close steam valve and 
open drain plug to allow steam to escape from cup; then close regulating 
valve, remove filling plug and fill cup with graphite. After replacing filling 
plug, close drain plug, open steam valve (wide) and regulate the feed of 
graphite by regulating valve. The sight feed glass can be cleaned by 
opening drain plug. If necessary to replace the sight feed glass, take cup 
apart by means of lock nut, and slide the new glass down through the 
opening. 

the same as the back steam pressure, these two forces 
will neutralize each other, and we have left, the posi- 
tive pressure of the column of water extending through 
the pipe P, the condenser and part of the pipe above 



138 AUDELS ANSWERS ON 

it, and the back pressure of the column of water in 
the sight feed glass. As the latter is much less than 
the positive pressure, the drop of oil is forced through 
the nozzle. As soon as it leaves the nozzle it is no 
longer acted upon by the positive pressure, and it 
rises through the water in the glass from the force of 
gravity, it being lighter than the water. After rising 
through the sight feed glass it floats through the tube 
T and through the support arm into the main steam- 
pipe and goes with the current of steam to the steam 
chest and cylinder. 

Ques. What is necessary for the operation of 
the lubricator? 

Ans. The positive pressure must always be greater 
than the back pressure. 

For instance, if a lubricator be connected to a horizontal 
steam pipe by being suspended below it, the back pressure would 
be greatly increased, and in order to get sufficient positive pres- 
sure the condensing pipe should rise 18 in. to 24 in. above the 
horizontal steam pipe and then descend to the condenser. This 
will give a column of water for positive pressure higher than the 
column of water which acts as back pressure. 

Ques. How should a lubricator be attached 
to the steam pipe? 

Ans. First drill and tap the steam pipe above the 
throttle, with ^-inch or J^-inch gas tap as may be 
required to receive support arm of the lubricator; 



PRACTICAL ENGINEERING 139 

insert the part containing the globe valve, after which 
couple the lubricator to it. Then tap the steam pipe 
about 18 inches or more above the top of the con- 
densing chamber, using i^-inch gas pipe for steam 
connecting tube which attaches to the top of the 
condenser. 




Fig. 68. — Screw feed marine grease cup. This cup is designed for the main 
bearings of marine engines, but will also be fjund suitable for other pur- 
poses where a screw feed is desired, such as for forcing grease some distance 
to the parts to be lubricated. 

If, for any reason, the steam pipe cannot be tapped 18 inches 
or more above the condensing chamber, it may be tapped lower 
down, and the tube of required length be bent into a horizontal 
coil. The action of the steam pipe which is tapped to receive 
the lubricator connections, should be extra heavy unless of 
large size, in order to secure proper thickness of metal to, form 
good joints. 



140 



AUDELS ANSWERS ON 



Ques. How is the lubricator figs. 64 and 65 
refilled ? 

Ans. Close valves A4 and A7. Open drain valve 
A8, then remove filler plug A3 and the water will 
drain out rapidly. When water is all out, close valve 
A8, fill with oil, and replace filler plug A3. Then open 




PlG. 69. — Nathan automatic grease cup. Directions for operating: When cup 
is empty, screw the plunger to top of reservoir, by means of the thumb nut C, 
unscrew and take off the reservoir and fill with grease, and, after screwing 
it back on the base, screw the jamb nut B up to the top so as to put the 
pressure of the spring on the grease. The base of the cup is provided with 
a simple feed regulating screw A, adjustable to suit any kind of grease. 



valve A4, and regulate the flow of oil with valve A7. 
The valve A9 is to be closed only when desiring to 
shut off steam from the lubricator in case of accidental 
breakage of the glass or when there is danger from 
freezing. Before starting the lubricator, time should 



PRACTICAL ENGINEERING 141 

be allowed for the sight feed glass and condensing 
chamber to fill with water from condensation. When 
there is danger from freezing when lubricator is not 
in use, empty the lubricator, and leave open valves 
A4, A8 and A6. Then close valve A9 and the small 
angle valve in condensing pipe above the lubricator. 

Ques. How is the feed started and regulated ? 

Ans. By valve A-7 (fig. 64). 



POINTS RELATING TO SIGHT FEED 
LUBRICATORS. 

1. — Before starting the lubricator, time should be allowed for 
the sight feed glass and condenser to fill with water. 

2. — When the sight feed glass fills with oil, the trouble is 
usually due to the condition of the nozzle below the glass. Some- 
times the upper part of this nozzle on the outside becomes covered 
with dirt or sediment from the oil. This makes the surface rough, 
and the drop will adhere to the nozzle much longer than if its 
surface was smooth. In consequence the drop becomes too large, 
and it is very liable to strike the side of the glass when rising and 
break, filling the glass with oil. To overcome this trouble take 
out the glass, clean off the dirt from the upper part of the nozzle, 
and rub it smooth. Then only drops of moderate size will form, 
and there will be no danger of them striking the side of the glass 
while rising. 



142 AUDELS ANSWERS ON 

3. — Do not use common rubber gaskets or cut glasses in sight 
feed lubricators. Both the gaskets and glasses in a lubricator 
have to withstand the action of heat and steam. The steam soon 
rots the common rubber gasket, causing it to leak, and cut glasses 
are very liable to crack and split from the ends as the result of 
the expansion and contraction due to the heat. A gasket made 
of alternate layers of linen and rubber is suitable. 

4.— Sometimes a lubricator cannot work because some of its 
small passages have become choked up with dirt from the oil. 
It is a good practice to occasionally empty the lubricator and 
blow steam through it so as to thoroughly clean out any dirt 
or sediment that may be lodging in the small tubes or passages. 

5. — When the engine is shut down, as during the noon hour, 
and the oil regulating valve closed, the water feed valve should 
be left open. If the water feed valve be left open it acts as a 
vent, and some of the water in the bottom of the body of the 
lubricator will be forced up into the condenser. If the oil regu- 
lating valve and the water feed valve be both shut there will 
be no outlet for the expanding oil, and it will soon exert such a 
pressure on the body as may cause it to bulge and even to burst. 
By attaching a pressure gauge to a lubricator, which had both 
water feed and oil regulating valves shut off while being acted 
upon by steam, a pressure of nearly 1,000 lbs. to the square inch 
was shown to be acting on the body of the lubricator. 



PRACTICAL ENGINEERING 143 

INSTALLATION and OPERATION 

OF 

ENGINES 



Ques. How should an engine foundation be 
built? 

Ans. The foundation should be built large and 
heavy enough to effectively prevent vibration, and 
should be independent of the building walls. It 
should be at least 25 per cent, larger in area at bot- 
tom than the area of engine bed plate. It should be 
built of stone or hard brick laid in the best Portland 
cement. The foundation bolts should go to within a 
foot of bottom of foundation and should have large 
plates or washers. The foundation should be amply 
seasoned before placing engine in position. 

Ques. How would you line up an engine? 

Ans. The cylinder is first bolted to the frame of 
engine, and if dowels be provided, it is easily lined 
up true with frame; if no dowels be provided, cylin- 
der must be so adjusted to frame that a line passing 
through center of cylinder will be exactly midway 



144 



AUDELS ANSWERS ON 




PRACTICAL ENGINEERING 145 

between the two guide bearings on frame. The pis- 
ton and rod and crosshead are now put in place, and 
the crosshead is adjusted on its shoes so that the 
piston rod will be exactly level at all parts of stroke. 
The crank shaft is now put in position and connec- 
ting rod put in place. When the engine is on either 
dead center the centers of piston rod, connecting rod 
and crank should be exactly in line, also the center of 
cylinder should be exactly in line with center of shaft. 
We now level the crank shaft carefully and install it 
exactly at right angles to the connecting rod, and the 
engine is properly lined up. 

Ones. How do we make a steam tight joint 
between cylinder and piston? 

Ans. All pistons are fitted with a cast iron or 
steel spring ring, which lays up tight against inside 
of cylinder; if sufficiently lubricated, both inside of 
cylinder and piston rings will wear as smooth as 
glass, and a steam tight joint is easily maintained. 
If engine be run long periods without oil, cylin- 
der walls will become rough and cut, and will leak 
steam. Usually too much oil is used. 

Ones. How does lubrication reduce friction? 

Ans. Lubrication reduces friction by keeping the 
bodies separated by a film of the lubricant, thus pre- 
venting their direct contact, and in substituting the 



146 AUDELS ANSWERS ON 

fluid friction of the particles of the lubricant for the 
friction of the solid bodies. 

Ques. What are the important qualities that 
a lubricant should possess ? 

Ans. 1, Body; 2, fluidity; 3, freedom from gum- 
ming ingredients ; 4, freedom from acidity; 5, stability 
under temperature changes; 6, freedom from foreign 
matter. 

Ques. What is understood by the term 
44 body of a lubricant?" 

Ans. The " body of a lubricant " indicates a 
certain consistency, or substance, that prevents it 
being squeezed out easily from between the moving 
bodies. 

Ques. What is understood by the term 
44 fluidity of the lubricant?" 

Ans. The fluidity of a lubricant refers to a certain 
lack of cohesion between the different particles of the 
substance, that reduces the fluid friction to a mini- 
mum. 

Ques. Why should lubricants be free from 
gumming ingredients? 

Ans. A lubricant that gums loses its fluidity 



PRACTICAL ENGINEERING 147 

easily, collects dust and grit, and thus increases fric- 
tion and wear and tear generally. 

Ques. Why should lubricants be free from 
acidity? 

Ans. A lubricant that holds free acid would 
attack the bearing surface, destroy its smoothness, 
increase friction and lead to frequent and costly 
repairs. 

Ques. Why should lubricants possess stabil- 
ity under temperature changes? 

Ans. Lubricants should retain their good qualities, 
even when used under high temperatures, as in steam 
cylinders or valve chests, or when used under low 
temperatures, as in ice machines or exposed winches 
and windlasses. They should not evaporate nor be 
decomposed by the heat, nor congeal by the cold, and 
should retain their normal body and fluidity as much 
as possible. 

Ques. Why should the lubricant be free from 
all foreign matter? 

Ans. Foreign matter will increase the friction, and 
clog the feeding tubes, thus leading to dangerous 
accidents. 

Ques. What determines mainly the choice 
of a lubricant for a given purpose? 

Ans. 1, Price; 2, pressure; velocity; 3, tempera- 
ture. 



148 AUDELS ANSWERS ON 

For heavy pressures the lubricant should have a good deal of 
body, while for light pressures this is not so important. 

For high speed the lubricant should possess good fluidity; for 
low speeds, less fluidity. 

For low temperatures light mineral oils are used, while heavy 
mineral oils are employed for high temperatures. 

Ques. Name some good lubricants for cyl- 
inders and valves. 

Ans. For cylinders and valves a good grade of 
cylinder oil having a high cold test should be used. 
Graphite or plumbago in powdered form is also 
largely used in cylinders. 

Ques. How do we lay up an engine, say for 
a year or more? 

Ans. The inside of cylinder and valve chest should 
be carefully drained and covered thickly with oil or 
grease; the piston should be worked back and forth 
after grease is applied to cylinder, so that the piston 
ring may become oiled and the grease spread all over 
the cylinder walls. The valve and the seat should 
be carefully oiled; all packing should be removed 
and piston rod and all moving and bright parts of 
engine should be thickly covered with grease to pro- 
tect them from rust. 

Ques. What is a gasket? 

Ans. A gasket is the packing placed between 
the boiler and handhole or manhole plate, or 



PRACTICAL ENGINEERING 149 

between the cylinder flanges of the engines so as to 
obtain a tight joint. 

Ques. Of what materials are packings made? 

Ans. Steam packing, for piston rods, etc., is 
usually made of rubber interwoven with some strong 
cloth fabric; water or hydraulic packing is made 
of braided flax or hemp for low pressures and 
from hemp and rubber for high pressure work. 
Metallic packing, made of babbitt metal, is used on 
the piston and valve rods of some engines. 

Ques. How do we find the necessary speed 
of a throttling governor to give the best results? 

Ans. The speed of a throttling governor depends 
altogether on the make, size and weight of the balls, 
no general rule can be given; the proper speed is 
always stamped on the governor. 

Ques. How do we re-babbitt a bearing? 

Ans. The shaft is placed in journal box after all 
the old babbitt metal has been chipped out and placed 
in its true running position and secured by blocks or 
hangers. Melted babbitt metal is now poured into 
the space between the journal box and the shaft; the 
shaft is now removed and the rough surface of the 
babbitt metal scraped off with a scraper or an old 
knife, and shaft may be put back in its place. Great 
care is necessary when heating babbitt metal so as 



150 AUDELS ANSWERS ON 

not to overheat or burn it; when it will char a dry, 
soft wooden stick it is at about the proper temperature 
for pouring. 

Ones. What is a speed indicator? 

Ans. A speed indicator is a small instrument used 
to find the number of revolutions a certain machine 
or shaft is making per minute; all speed indicators 
have a bayonet pointed shaft which may be inserted 
into the center hole in end of shaft and the speed that 
shaft runs is recorded on a graduated dial. 

Ques. What is a condenser? 

Ans. A condenser is an apparatus used on engines 
to reduce the back pressure due to the exhaust and 
atmospheric pressure. 



PRACTICAL ENGINEERING 151 



STEAM PUMPS 



Ques. What is a steam pump? 

Ans. A steam pump is a machine for pumping 
water against any desired pressure. 

Ques. How high will a pump lift water? 

Ans. When in perfect condition and if the suc- 
tion pipe is tight a pump will lift water almost 34 
feet. 

Ques. Why do you say if the suction pipe be 
tight? 

Ans. Because a very small leak in the suction 
pipe would reduce the vacuum, and the pump would 
not lift the water so high. 

Ques. Is it practical to install a pump in such 
a manner that the suction lift will be 34 feet? 

Ans. No; no pump should be made to lift water 
more than about 24 feet. 

Ques. Will a duplex pump lift water higher 
than a simple pump? 

Ans. No. 



152 AUDELS ANSWERS ON 

Ques. Against what pressure will a pump 
work? 

Ans. There is practically no limit of the pres- 
sure against which a pump will deliver water; we are 
only limited by the strength of the water end of 
pump; some hydraulic presses require pumps that 
will pump against a pressure of 30,000 pounds per 
square inch. 

Ques. Why will a pump not lift hot water as 
well as cold water? 

Ans. When the lift is considerable and the water 
hotter than about 140 degrees, vapor will fill the 
water cylinders of pump and this vapor is simply 
compressed and not expelled by the action of the 
plungers. When a pump must handle hot water it 
should get the water under a head; that is, the water 
should flow into the pump by gravity. 

Ques. Which cylinder should be the larger 
in a boiler feed pump? 

Ans. The steam cylinder should have considerably 
more area than the water cylinder on any boiler feed 
pump. 

Ques. Why must the steam cylinder be so 
much larger? 

Ans. Because if the pistons were of the same 
size the resistance offered by the water in discharge 



PRACTICAL ENGINEERING 153 

pipe would be equal to the total force on the steam 
piston; to overcome this resistance and the internal 
friction in pump, which is considerable, and the fric- 
tion of water in suction and delivery pipe, it is neces- 
sary for steam pistons to be considerably larger 
than the water pistons. 

Ques. What may be said of single or simple 
pumps? 

Ans. All single cylinder pumps have a somewhat 
complicated valve gear ; all have two and some makes 
have three steam valves for each cylinder, while in 
the duplex pump we have but one simple slide valve 
for each cylinder. 

Ques. What is a compound pump? 

Ans. A compound pump may be either simple 
or duplex and has two sets of steam cylinders placed 
one back of the other. The larger cylinder is driven 
from the exhaust of the smaller cylinder. 

Ques. Are any pumps made which have 
larger water cylinders than steam cylinders? 

Ans. Yes; pumps used for light service; where 
a large quantity of water is to be pumped against a 
very light pressure the water piston may have 
more area than the steam piston. 

Ques. What is an elevator pump? 

Ans. A pump designed to pump against a heavy 
pressure used chiefly for hydraulic elevator service. 



154 



AUDELS ANSWERS ON 




Fig. 73. — The Knowles pump. A piston valve G in the steam chest moves the 
main valve. This valve piston is driven alternately backward and forward 
by the pressure of steam, carrying with it the main valve, which admits 
steam to the main steam piston that operates the pump. The main valve is 
a plain slide whose section is of B form, working on a flat seat. The valve pis- 
ton is slightly rotated back and forth by the rocker bar, H ; this rotative move- 
ment places the small steam ports D E F, fig. 74., which are located in the 
under side of the valve piston in proper position with reference to the cor- 
responding ports, A B, cut in the steam chest. Steam enters through the 
port at one end and fills the space between the valve piston and the head, 
drives the valve piston to the end of its stroke and carries the rr ain slide 
valve with it. When the valve piston has traveled a certain distance, a 
corresponding port in the opposite end is uncovered and steam enters, 
stopping its progress by giving it the necessary cushion. The piston rod 
with its tappet arm, J, fig. 73, moves backward and forward with the 
piston. At the lower part of this tappet arm is attached a stud or bolt, K, 
on which is a friction roller, I. This friction roller, lowered or raised, adjusts 
the pump for a longer or shorter stroke. This roller coming in contact with 
the rocker bar at the end of each stroke, and this motion is transmitted to 
the valve stem, causing the valve to roll slightly. This action opens the 
ports, admits steam and moves the valve piston, which carries with it the 
main slide valve which admits steam to the main piston. The upper end 
of the tappet arm does not come in contact with the tappets, L M, on the 
valve rod, unless the steam pressure from any cause should fail to move the 
valve piston, in which case the tappet arm moves it mechanically. 



PRACTICAL ENGINEERING 



155 



Ques. What is an underwriters' or fire 
pump? 

Ans. A pump installed in large factories and 
high buildings to supply fire lines and stand pipes 
in case of fire. 

Ques. What is a centrifugal pump? 

Ans. A rotary pump somewhat resembling a 
blower in appearance; no valves being required in 
this pump, it is valuable in pumping sewerage and 
other liquids containing sand, gravel or mud. 








ABC 
Fig. 74. — Valve details of Knowles single pump as described in fig. 73. 



Ques. What is a "high duty" pump? 

Ans. A pump having a fly wheel or equivalent in 
connection with a valve gear designed to secure an 
early cut off, so as to work the steam expansively 
and thus obtain greater economy than that of the 
ordinary type of pump which takes steam at full stroke. 

Ques. What economy will a compound pump 
have over a simple pump? 

Ans. About 20 per cent, more or less depending 
upon operating conditions. 



156 



AUDELS ANSWERS ON 



Ques. How do we set the steam valves of a 
duplex steam pump? 

Ans. Place both piston rods of pump in mid posi- 
tion; when this is done both levers which engage the 



r\ 




Pig. 75. — Duplex pump with inside packed plungers. In construction, two 
steam pumps are placed side by side and so combined that one piston acts 
to give steam to the other, after which it finishes its own stroke and waits for 
its valve to be acted upon by the other pump before it can renew its position. 
This pause allows the water valves to seat quickly, and removes any harsh- 
ness of motion. As one or the other of the steam valves is always open, 
there is no dead point, and therefore the pump is always ready to start when 
the steam is admitted. 



spools on piston rod will be in exactly a vertical 
position. Now place the valves in mid-position, 
that is, place them so that they will just cover both 
steam ports. Now connect the valve rods and links 



PRACTICAL ENGINEERING 157 

in such a way that the lost motion will be exactly 
divided and the valves are properly set. 



How to Set the Valves of a Duplex Pump, 



Rule. — I. Locate the steam piston in the center of the cylinder, 
as in fig. 75. This is accomplished by pushing the piston to 
one end of its stroke against the cylinder head and marking the 
rod with a scriber at the face of the stuffing box, and then bring- 
ing the piston in contact with the opposite head; 

II. Divide exactly the length of this contact stroke. Shove the 
piston back to this half mark, which brings the piston directly 
in the center of the steam cylinder; 

III. Perform the same operation with the other side] 

IV. Place the slide valves, which have no lap, to cover all the 
ports; 

V. Pass the valve stem through the stuffing box and gland. The 
operation of placing the pistons in the center of their cylinders 
brings the levers and rock shafts in a vertical position; 

VI. Screw the valve stem through the nuts until the hole in the 
the eye of the valve stem head comes in a line with the hole in 
the links, connecting the rocker shaft ; then put the pins in their 
places ; 

VII. Adjust the nuts on both sides of the lugs of the valves to 
leave about yi" or Y%" loss motion on each side. 



158 AUDELS ANSWERS ON 

This process of adjustment being performed with both cylin- 
ders, the steam valves are set. In short the travel of the two 
valves is simply equalized. 

Ques. Why do we give the valves lost motion 
in a pump of this type? 

Ans. The lost motion has very much to do with 
the popularity of this style of pump. When the pis- 
ton reaches the end of stroke this lost motion must 
be taken up, which causes the pump to pause slightly 
before beginning the return stroke; this slight pause 
allows the water valves to seat properly and noise- 
lessly and gives the pump a smooth action through- 
out the entire stroke. 

Ques. Where is this lost motion placed? 

Ans. On most pumps inside the steam chests; 
on some pumps it is outside where it may be adjusted 
while pump is running. 

Ones. Does this lost motion ever have to 
be reduced to make the pump work prop- 
erly? 

Ans. Yes; when the links and motion pins be- 
come worn they have the same effect on the pump as 
though the lost motion in valve was increased, and 
the remedy is either new links and pins or reducing 
the lost motion in valve gear, which may be done by 



PRACTICAL ENGINEERING 159 

fitting a washer between the valve nut and the lugs 
on valve. 

Ones. When the levers that engage the spools 
on piston rod become worn, how may they be 
made as good as new? 

Ans. They should be taken out, heated and 
spread with a hammer; they may now be filed and 
carefully rounded to fit between the shoulders of 
spool and put back. 

Ones. When the slide valves of duplex pumps 
leak badly, what should be done? 

Ans. They should be taken out, ground or filed 
true; the valve seats will also have to be filed and 
scraped true. 

Ques. If new rings were put on steam pis- 
ton and we found that it still leaked steam 
badly, where would you look for the trouble? 

Ans. We would find that the piston body and fol- 
lower had become worn at the face where they touch 
the rings and that steam passed over piston under 
the ring and over follower; the proper remedy would 
be to file the distance piece cast on piston body so 
that the ring will fit snugly between piston and fol- 
lower. 



160 AUDELS ANSWERS ON 

Ques. How many ports has a duplex 

pump? 

Ans. Five; the steam and exhaust ports are sep- 
arate in this style of pump; the exhaust ports are 
those placed nearest the center of the cylinder and are 
covered or closed by the piston just before the end of 
the stroke, whereby a portion of the exhaust steam is 



Fig. 76. — A very small Worthington duplex pump. Its dimensions are as fol- 
lows: 2-inch diam. steam cylinder; lj^-inch water cylinder; 2%-inch 
stroke. Its capacity is .044 gallons per revolution; rev. per minute, 80; 
gallons per minute, 3.5. Steam pipe, %-inch; exhaust pipe, K-inch; suc- 
tion pipe, 1-inch; discharge, 24-inch. Floor space occupied, 1' 9" x 7" 
wide. 



trapped and made to act as a cushion between the 
piston and cylinder head. This assists materially in 
the smooth operation of the pump. 

Ques. How many water valves has a duplex 
pump? 

Ans. Eight; four suction and four discharge 
valves. 



PRACTICAL ENGINEERING 161 

Ques. Of what material are the water valves 
made? 

Ans. For low pressure of hard rubber; for hot 
water and high pressure they are preferably made of 
brass. 

Ques. What is the difference between a 
plunger and a piston? 

Ans. A plunger is a solid cylindrical body which 
fits accurately or approximately the chamber within 
which it reciprocates. It differs from a piston in that 
it is longer than its stroke. A plunger is guided by a 
stuffing box, either internal or external, while a piston 
is guided by the cylinder walls. 

The term plunger is aften erroneously used for piston ; the dis- 
tinction should be carefully noted. 

Ones. Why is a duplex pump not as econ- 
omical in the use of steam as a power pump? 

Ans. Because all duplex pumps take steam full 
stroke, therefore there is no expansive benefits de- 
rived. 

Ques. How are the water cylinders of steam 
pumps lined? 

Ans. The water cylinders are bored out somewhat 
larger than the size of plunger; a brass or composi- 
tion sleeve is forced into the cylinder by a pulling 
screw or by a hydraulic ram. 



162 



AUDELS ANSWERS ON 




Fig. 77.-Method of piping a pump. The figure represents the pipe 
connections, etc., of a pump with the suction and discharge 
openings on the opposite sides. D represents the foot valve and 
strainer placed on the lower end of the suction, which should 
be not less than a foot from the bottom of the well; C is the 
suction pipe proper, screwed into the elbow, E, leading to 
the suction chamber, which contains the strainer, A. In 
connecting large pumps it is customary to attach a vacuum 
chamber, F, which in the absence of any regular pattern, 
may be made of a piece of pipe of the same diameter as the suction and 
screwed into a T, instead of the elbow, E, with a regulation screwed cap on 
top as shown in the dotted lines. A priming pipe is shown by the letter J, 
often used to fill the pump on starting. The discharge pipe connection is 
shown at G with the air chamber attached. 







PRACTICAL ENGINEERING 163 

Ques. What type of pump has all the advan- 
tages of the duplex pump and is more economi- 
cal to use? 

Ans. A power pump which is driven by a belt 
from the engine, we naturally get some expansive 
benefits of the extra steam used in engine to drive 
pump; the speed of a power pump, of course, can- 
not be regulated, so we keep the water in boilers at 
the desired level by connecting a bypass between suc- 
tion and delivery pipe provided with a valve with 
which we can send as much water as is not needed 
back into suction pipe of pump. 

Ones. Of what use is an air chamber on a 
pump? 

Ans. It causes the pump to deliver the water in 
a steady stream; when pumps are obliged to lift the 
water more than 8 feet, an air chamber should also 
be placed on suction pipe. 

Ones. How should the pipes be arranged on 
pumps? 

Ans. They should have as few bends and sharp 
turns as possible; elbows and tees in a pipe line 
greatly increase the friction. 

Ones. How do we find the pressure of a 
column of water of any height? 

Ans. By multiplying the height in feet by the 
constant .434. 



164 AUDELS ANSWERS ON 

Ques. How do we find the number of gallons 
of water a pump will supply per hour? 

Ans. From the following formula: 

diameter 2 X • 7854 X strokes per minute X 60 
2oT = § als - P er nour • 

The diameter and stroke is taken in inches. 

The numerator is divided by 231 because 1 gal. = 231 cu. ins. 

Ques. In selecting a pump for a certain sized 
boiler, how large a pump would you select? 

Ans. I would select a pump capable of supplying 
about 60 pounds or about 7 gallons of water per 
hour, for every horse power developed by boiler ; this 
would be just twice as much water as the boiler 
would need, but boiler feed pumps should be plenty 
large, as much water is wasted through leaks in 
pipes, packing, etc. The pump should be capable of 
supplying the above amount of water when running 
at a moderate speed. 

Ones. How do we find the horse power a 
pump is developing in pumping a certain 
amount of water a certain height? 

Ans. By multiplying the weight of water pumped 
in pounds by the perpendicular height it is raised, 
in feet per minute, and dividing the product by 
33,000. 



PRACTICAL ENGINEERING 165 



INJECTORS 



Ques. What is an injector? 

Ans. An injector is an instrument for forcing 
water into a boiler against the boiler pressure. Some 
boilers depend altogether on one or more injectors 
for feeding; others have and use an injector as an 
auxiliary feed. 

Ques. Describe briefly how an injector works. 

Ans. Dry steam from the upper part of the 
boiler is led into the injector and made to flow through 
a contracted tube; at a short distance from the 
end of this contracted tube is placed another tube 
which gradually increases in diameter. The space 
around and between the two tubes forms a chamber 
which is in communication with the suction pipe. 
Steam coming from the boiler at a great velocity will 
shoot across the small gap between the two tubes and 
create a partial vacuum in the suction chamber and 



166 



AUDELS ANSWERS ON 



cause the water to flow into the injector and mix 
with the steam ; when first started this water and steam 
will escape through the overflow pipe, and when we 
get a steady stream we close the overflow valve and 
the water and steam are forced into the boiler. In 




Fig. 78. — Principle of the injector. Steam is led from the boiler through pipe A» 
which terminates in a nozzle surrounded by a cone E, connected by the pipe 
B with the water tank. When steam is turned on it rushes with great 
velocity from the nozzle, and creates a partial vacuum in cone, E, which 
soon fills with water. On meeting the water the steam condenses, but not 
before it has imparted some of its velocity to the water, which thus gains 
sufficient momentum to force open the check valve and flow through pipe D 
to the boiler. The overflow space O O between E and C allows steam and 
water to escape until the water has gathered the requisite momentum. An 
important condition which must be fulfilled, in order that the injector will 
work, is that the supply of water be sufficient to condense the steam. The 
efficiency of the injector as a boiler feeder is 100% less the trifling loss due 
to radiation; however, the injector is not the most economical boiler feeder 
because it can draw only cold or moderately warm water, while a pump can 
draw water heated by exhaust steam, which otherwise would be wasted. 



PRACTICAL ENGINEERING 



167 



any of the automatic types of injector the overflow 
valve is closed automatically and to start an injector 
of this type all that is necessary is to open steam and 
water valves. 




Fig. 79. — Sectional view of the Korting double tube injector. The lower tube 
is for lifting the water to the injector, and the upper tube for forcing the 
water in the boiler. A is the closed position of the operating handle. To 
start the injector, the handle is moved slowly in the direction D. 



Ques. 
tor? 



State the principle of the injec- 



Ans. An injector forces water into the boiler be- 
cause the kinetic energy of a jet of steam is much 
greater than that of a jet of water escaping under 
the same conditions. 



168 AUDELS ANSWERS ON 

Ques. Will an injector handle hot water? 

Ans. Yes, if not too hot, the average injector will 
handle water up to about 140 degrees F., but its ca- 
pacity will be somewhat reduced. The best results 
are obtained when the temperature of the water is 
about 50 degrees F. 

Ones. What advantage is there in feeding 
boilers with an injector? 

Ans. There are practically no heat losses; all the 
steam used to operate the injector is returned to the 
boiler and the only heat loss is from radiation, 
which is very small. 

Ones. What is the best way to connect up 
an injector? 

Ans. Injectors should preferably take water from 
a tank instead of the city mains and should be placed 
directly over the tank so that the overflow may be 
watched when starting the instrument. This tank 
should be supplied from the city mains and should 
be fitted with a float valve so that the tank will al- 
ways remain full. Satisfactory results, however, may 
be obtained by direct connection with city main by 
regulating the supply with a valve. 

Ques. If an injector fail to work, what is 
usually the cause? 

Ans. The strainer on suction pipe may be clogged, 
or there may be a bad leak in the suction pipe; 
sometimes a small chip or a piece of scale will pass the 



PRACTICAL ENGINEERING 169 

strainer and will lodge in the contracted opening of 
the forcing tube, or some foreign matter may have 
lodged between the overflow valve and seat, pre- 
venting its closing. 

Ones. At how low a pressure will an in- 
jector work? 

Ans. About 30 pounds, although some injectors 
will work well on 20 pounds of steam or less. 

The author, by very careful adjustment of the steam and 
water valves, has succeeded in operating a single tube injector 
with only 5 lbs. steam pressure. 

Ques. How high will an injector ordinarily 
lift water? 

Ans. A well constructed injector will lift water at 
least 15 feet. 



170 AUDELS ANSWERS ON 



FEED WATER 
HEATERS 



Ques. What is a feed water heater? 

Ans. A contrivance by which the feed water is 
heated before it enters the boiler. 

Ques. How many types of heater are there? 

Ans. Two types: the open and closed feed water 
heater. 

Ques. How is an open heater constructed? 

Ans. An open heater is simply a tank kept about 
half full of water by a float valve on a water pipe from 
city mains; the exhaust steam from the engine blows 
into this tank and heats the water very hot ; the boiler 
feed pump takes its suction from this tank, which 
should be placed above the pump so that the pump 
will get the water under a head. This form of heater 
has the advantage of imparting somewhat more heat 



PRACTICAL ENGINEERING 



171 



to the water than does the closed type because the 
feed water and the exhaust steam come in direct 
contact. With this form of heater the feed pump 
will have to pump hot water, which is undesirable; 
also, more or less oil passes through the filter with 
the water and is deposited in the boiler forming a 
hard scale. 




tYHAusr ouner 








Figs. 80 and 81. — Open and closed feed water heaters. In the open heater, 
fig. 80, the steam raises the temperature of the water by mingling with it, 
that is, by direct contact. The closed type of heater resembles a surface 
condenser; the exhaust steam surrounds copper or brass tubes which 
contain water, or the water circulates about tubes through which steam 
passes. Fig. 81 shows a feed water heater, of the closed type, the exhaust 
steam heating the feed water within the tubes. 



172 AUDELS ANSWERS ON 

Ques. How is a closed feed water heater 
built? 

Ans. The closed feed water heater consists of a 
closed tank provided with a coil, or a great number 
of small tubes; the exhaust steam passes through the 
tank and heats the feed water, which is contained in 
the coil or tubes. In this style of heater the steam 
and water do not mix, and the pump only has to 
pump cold water, as this style of heater is always 
placed between pump and the boiler. 

Ones. How should the piping be arranged on 
a closed heater? 

Ans. A valve should be placed on the pipe enter- 
ing heater and a valve should be on pipe leaving 
heater; a by pass pipe should be connected between 
the supply and delivery pipe so that heater may be 
opened for inspection or repair without interrupting 
the service. 

Ques. What economy is due to heating the 
feed water? 

Ans. There is a saving of about 1 per cent, for 
each 11° F. increase in the temperature of the feed 
water. 



PRACTICAL ENGINEERING 173 



STEAM HEATING 



Ones. What systems of steam heating are 
in general use? 

Ans. There are two systems of steam heating in 
general use, the one pipe system and the two pipe 
system. 

Ones. How does the single pipe system work? 

Ans. In this system of steam heating, only one 
pipe is necessary and the return end of radiator is 
permanently plugged up. Great care must be taken 
in the design and installation of a system of this 
kind to have all the horizontal pipes throughout the 
building drain towards the boiler. Another requisite 
is that all risers must have large drip pipes con- 
nected to bottom of them, which lead into the pump 
governor or receiver ; as all the condensed water from 
radiators must fall to bottom of riser in this system 
all horizontal pipes above the boiler room floor should 
be as short as possible, which means that a greater 



174 



AUDELS ANSWERS ON 



number of risers are necessary. The principle on 
which this system works is as follows. Steam is 
turned on from the boiler and in a short time the 
pipes are filled with steam at the desired pressure. 



S"*-| 



VALVL 




Fig. 82. — One pipe system of steam heating. The steam rising from the boiling 
water passes through the top opening of the boiler into the feed pipe, travels 
to the radiators, where it gives up its heat, is condensed by being turned 
back to water, and returns to the boiler through the return pipe, entering 
it at the side near the bottom. 



The arrangement of the piping permits the condensed 
water to drop back and down the riser and to be 
carried through the drip pipe to pump governor or 



PRACTICAL ENGINEERING 175 

back to boiler, although the steam is flowing in the 
opposite direction to replace the steam condensed. 
As in the two pipe system, an air pipe is frequently 
added, but if an automatic air valve be used, the air 
pipe may be dispensed with. 

Ques. How does the two pipe system work? 

Ans. Steam from the boilers is led up through 
the building to be heated through a riser having 
outlets on each floor for connecting the radiators. 
The returns from the radiators are piped back to the 
boiler or pump governor by a separate pipe; some- 
times a small air pipe is added to keep the radiator 
from becoming air bound. 

Ques. What system is the better, the single 
or two pipe system? 

Ans. The single pipe system, if properly installed, 
will give as good results as the two pipe system, and 
only one-half the number of valves and pipes though 
larger sizes are required. 

Ques. What is a gravity heating system? 

Ans. In the gravity heating system no pump or 
pump governor is used. The returns from the radia- 
tors are returned to boiler by gravity, hence its 
name; this system is suitable only for small heating 
plants. 



176 AUDELS ANSWERS ON 

Owes. Explain why radiators become air 
bound ? 

Ans. Radiators become air bound because when 
turned off and full of steam, the steam will rapidly 
condense and a vacuum will be created in the radiator ; 
this vacuum will be broken by numerous small leaks 
in piping and through packing of valves, etc. If 
the radiator remain turned off for a long time it 
will fill with air and this air must be expelled so that 
steam may take its place. Air also is contained in 
the water. 

Ques. How does an automatic air valve work? 

Ans. Automatic air valves have long composition 
stems which when cold, contract and open valve 
and let out the air; as soon as steam reaches the 
valve stem, it will expand and close valve. 

Ques. Is it more economical to heat a build- 
ing with low or high pressure steam? 

Ans. Low pressure is more economical; very few 
buildings require more than ten pounds pressure for 
heating; some of the largest buildings are heated 
with three pounds of steam in extreme cold weather. 

Ques. How do we know what pressure is on 
radiators? 

Ans. Every heating system should have a steam 
gauge connected to main heating pipe as near the 
reducing valve as possible. 



PRACTICAL ENGINEERING 177 

Ques. When a building is heated by steam 
from a high pressure boiler, how do we main- 
tain a constant pressure on the radiators? 

Ans. By the use of a reducing valve, which is a 
double seated valve of such construction that any 
desired pressure may be carried on the low side of 
valve. 

Ques. How much space will a square foot of 
radiating surface heat? 

Ans. About 70 cu. ft. in outer or front rooms and 
100 cu. ft. in inner rooms. 

Ones. How many square feet of radiating 
surface will a square foot of boiler heating 
surface supply? 

Ans. From 7 to 10 square feet. 

Ones. Should a pump governor be fitted 
with a blow off? 

Ans. Yes, as the oils from engine and pumps 
will float on the top of water in receiver and by 
closing the main return valve this oil may be blown 
into sewer; otherwise it would eventually find its 
way into the boiler and cause trouble. 

Ques. How much space will one horse 
power heat in ordinary city buildings? 

Ans. From 10,000 to 20,000 cubic feet, depending 
on the amount of glass surface exposed to the open 
air. 



178 AUDELS ANSWERS ON 

Ques. Is it proper to heat a building with 
exhaust steam from engines and pumps? 

Ans. Yes, it is, and a very large amount can be 
saved by so doing. 

Ques. What is the chief objection made to 
using exhaust steam for heating? 

Ans. The chief objection is that the whole system 
will become coated with oil on inside, and that a 
large quantity of oil will be returned to the boilers 
with the returns. Plants using exhaust steam for 
heating should be provided with a water purifier or 
grease extractor. 

Ques. How do we force the exhaust steam 
through the radiators? 

Ans. By putting a back pressure valve on or near 
the top of exhaust pipe and tapping the exhaust pipe 
on every floor for radiator or coil connections. 

Ques. May not this back pressure valve be 
connected to exhaust pipe near the engine 
instead of just under or on roof? 

Ans. Yes, but in this case a separate riser is 
necessary; when installed on or just under the roof 
of building the exhaust pipe may also be used as a 
riser by providing outlets at each floor. 



PRACTICAL ENGINEERING 



179 



Ques. How should a building be piped for 
exhaust heating? 

Ans. The piping throughout should be about 30 
per cent, larger in area. 




Fig. 83. — American Ball angle compound engine connected to an exhaust 
steam heating system. The exhaust pipe is extended to the roof, and a 
relief valve attached which prevents the back pressure exceeding that for 
which the valve is set. Small pipes lead from the large horizontal distribu- 
tion pipe to the receiver into which the condensation drains: these pipes 
are connected with the radiators at intermediate points are shown. A pump, 
shown at the left, returns the condensation to the boiler. 



180 AUDELS ANSWERS ON 

Ques. How does a pump governor work? 

Ans. A pump governor or receiver, as it is 
sometimes called, is simply a closed tank and should 
set below the lowest radiator or heating coil and 
enough above the pump so that the water will flow 
freely from receiver into pump. The returns from 
the entire heating system flow into the bottom of the 
receiver, which is fitted with a float valve controlling 
the steam to pump. When the receiver is nearly full 
of water the float will raise and open valve, admitting 
high pressure steam from boiler to pump, and it will 
keep the pump running at such a speed to just keep 
the water in the pump governor or receiver at a cer- 
tain level. In order that the pump governor may not 
become air or steam bound they are usually fitted at 
the top with a pipe leading to the low pressure side 
of main steam pipe. The extra water necessary to 
maintain a constant water line in the boilers is pro- 
vided by tapping a small pipe into governor from the 
city mains and the water line in boilers is maintained 
constant by regulating this valve and not by manipu- 
lating throttle valve on pump. 



PRACTICAL ENGINEERING 181 



STEAM TRAPS 



Ques. What is a steam trap? 

Ans. A steam trap is a device in which the water 
of condensation is drained out of a radiator hot water 
tank or other steam appliance without permitting any 
live steam to escape. 

Ques. Is a steam trap ever connected to a 
steam engine? 

Ans. Yes ; steam traps are sometimes placed under 
the cylinders of engines and the cylinder drips are 
connected to trap to keep cylinder free of water ; when 
this is done the drip valves may remain open when 
engine is running. 

Ones. How may traps be divided? 

Ans. There are two kinds of trap, float traps and 
expansion traps; the float trap depends upon a float 
to open and close a valve to expel the accumulated 



182 



AUDELS ANSWERS ON 



water, while in the expansion trap the valve is opened 
and closed by a rod which expands and contracts. 

BY PA55 VALVE 



OUTLET 




Fig. 84. — Steam trap in operation. As water of condensation collects in the 
receiver, the float rises and opens the valve at the left, thus allowing the 
water to escape. As the water level recedes the float closes the valve, hence 
there is no escape of steam. 

Ques. Will a common trap return the con- 
densed water back into the boiler? 

Ans. No; a common trap will only work against 
about one-quarter the boiler pressure. 



PRACTICAL ENGINEERING 



183 




DRIP 



Fig. 85. — Separator with receiver and water gauge glass for showing the height 
of the separated water in the receiver. In operation, the entrained water 
carried along with the steam is separated from the steam by centrifugal force; 
that is, the separator is arranged to suddenly change the direction of the 
steam, thus throwing out the entrained water and delivering to the engine 
almost dry steam. 



184 AUDELS ANSWERS ON 

Ques. What is a by pass on a trap? 

Ans. A small valve which we may open to start 
the trap or which may be opened when a very large 
amount of water is to be discharged; this valve al- 
lows the water to flow directly into the waste or 
sewer pipe without passing through the float valve; 
the by pass should always be closed as soon as trap 
becomes hot. 

Ques. Should a trap be placed near a coil or 
radiator? 

Ans. Yes, a trap should be placed as close as 
possible to the tank or coil that it drains. 



PRACTICAL ENGINEERING 185 



BELTS, GEARS, AND 
PULLEYS 



Ques. How should belts be run? 

Ans. Whenever possible belts should be run with 
the tight side on the bottom, the upper or loose side 
will then form a concave arc, which increases the 
arc of contact on both pulleys; a belt put on in this 
manner may be kept much slacker than a belt put on 
the reverse way. 

Ques. What is a quarter turn belt? 

Ans. A quarter turn belt is used to drive a shaft 
that is at right angles to .the driving shaft; as, for 
example, a vertical shaft driving a horizontal shaft. 

Ques. What is a cross belt? 

Ans. A cross belt is used to drive a shaft in the 
reverse direction of the driver. 

Ques. Which will pull more: an open belt 
or a cross belt? 

Ans. A cross belt will pull more, as by crossing we 
increase the arc of contact (belt surface on pulley). 



186 AUDELS ANSWERS ON 

Ones. How do we find the diameter of pul- 
ley required on engine to run a dynamo at a 
speed of 1,450 revolutions per minute the 
dynamo pulley being 10 inches in diameter 
and the speed of engine is 275 revolutions per 
minute? 

Ans. The diameter of pulley required on engine 
will be 

10 X — =53 inches, nearly. 

275 

To find the diameter of the driving pulley, multiply 
the speed of the driven pulley by its diameter, divide 
the product by the speed of the drive and the answer 
will be the size of the driver required. 

Ones. If the speed of engine be 325 revolu- 
tions per minute, diameter of engine wheel 42 
inches, and the speed of the dynamo 1,400 
revolutions per minute, how large a pulley is 
required on dynamo? 

Ans. The size of the dynamo pulley will be 

42 X -^- =9% inches. 
1,400 

If the size of dynamo pulley is to be found, multiply 
the speed of engine by the diameter of engine wheel 
and divide the product by the speed of the dynamo. 



PRACTICAL ENGINEERING 187 

Ques. If a steam engine, running 300 revo- 
lutions per minute, have a belt wheel 48 inches 
in diameter, and be belted to a dynamo having 
a pulley 12 inches in diameter, how many 
revolutions per minute will the dynamo make? 

Ans. The speed of dynamo will be 

48 
300 X — = 1,200 rev. per mm. 
12 

When the speed of the driving pulley and its diameter 
are known, and the diameter of the driven pulley is 
known, we find the speed of the driven pulley by 
multiplying the speed of the driver by its diameter in 
inches and dividing the product by the diameter of 
the driven pulley. 

Ques. What will be the required speed of an 
engine having a belt wheel 46 inches in diam- 
eter to run a dynamo 1,500 revolutions per 
minute, the dynamo pulley is 11 inches in 
diameter? 

Ans. The speed of engine will be 

1,500 X —=359 r. p. m., nearly. 
46 

To find the speed of engine multiply the dynamo 
speed by the diameter of its pulley and divide by the 
diameter of engine pulley. 



188 AUDELS ANSWERS ON 

Ones. How much horse power will a belt 
transmit? 

Ans. The capacity of a belt depends on, its width, 
speed, and thickness. A single belt one inch wide and 
travelling 1,000 feet per minute will transmit one horse 
power; a double belt under the same conditions will 
transmit two horse power. 

This corresponds to a working pull of 33 and 66 lbs. per inch 
of width respectively. 

Ques. At what velocity should a belt be run? 

Ans. At from 3,000 to 5,000 feet per minute. 

Ques. How are the diameters and speeds of 
gear wheels figured? 

Ans. The same as belted wheels, only we use the 
number of teeth in gear instead of the diameter in 
inches. 



PRACTICAL ENGINEERING 189 



STEAM TURBINES 



A turbine is a machine in which a rotary motion is 
obtained by transference of the momentum of a fluid 
or gas. In general the fluid is guided by fixed blades, 
attached to a casing, and, impinging on other blades 
mounted on a drum or shaft, causing the latter to 
revolve. 

Turbines are classed various ways: They are 
classed as : 1 , radial flow, when the steam enters near 
the center and escapes toward the circumference ; and 
2, parallel flow, when the steam travels axially or 
parallel to the length of the turning body. 

Turbines are commonly, yet erroneously classed as : 

1. Impulse; 

2. Reaction. 

Ques. What is the distinction between these 
two types? 

Ans. In the so called impulse type, steam enters 
and leaves the passages between the vanes at the same 



190 



AUDELS ANSWERS ON 



pressure. In the so called reaction type, the pressure 
is less on the exit side of the vanes than on the entrance 
side. 

Fig. 86 is a sectional view of the Parsons- Westinghouse 
parallel flow turbine. Steam from the boiler enters first a re- 
ceiver in which are the governor controlled admission valves. 
These valves are actuated by a centrifugal governor. 




Fig. 86. — The Parsons-Westinghouse turbine. 



Steam does not enter the turbine in a continuous blast, but inter- 
mittently, or in puffs. The speed regulation is therefore accom- 
plished by proportioning the duration of these puffs to the load 
of the engine, this being effected by the governor, fig. 87. 

The governor of the turbine has only to move a small pilot 
valve, or slide, E, which admits steam under the piston F, and 
lifts the throttle valve proper off its seat. 

As soon as the pilot valve closes, the spring shuts the main 
throttle valve. Thus, at light loads, the main throttle or ad- 
mission valve is continually opening and shutting at uniform 
intervals, the length of time during which it remains open de- 
pending upon the load. 



PRACTICAL ENGINEERING 



191 



As the load increases, the duration of the valve opening also 
increases, until at full load the valve does not reach its seat at 
all and the steam flows steadily through the turbine. The steam 
thus admitted flows into the annular passage A, fig. 86, by the 
opening S, and then past the blades, revolving the rotor. 

When the load increases above the normal rated amount, a 
secondary pilot valve is moved by the same means, this in turn 
admitting steam to a piston, similar to F, which lifts another 




Fig. 87. — Governor of the Parsons-Westinghouse turbine. 



throttle valve. This admits steam into the annular space I, so 
that it acts upon the larger diameter of the drum or rotor, giving 
largely increased power for the time being. 

The levers or arms of the governor are mounted upon knife 
edges instead of pins, making it extremely sensitive. The ten- 
sion spring may be adjusted by hand while the turbine is running. 

The governor does not actually move the pilot valve, but shifts 
the point L in fig. 87. A reciprocating motion is given to the 
rod I by a small eccentric on the governor shaft; this is driven 
by worm gearing shown near O in fig. 86, so that the eccentric 
makes one revolution to about eight of the turbine. Thus, with 
a turbine running 1,200 revolutions, the rod I would be moved 



192 AUDELS ANSWERS ON 

up and down 150 times per minute. As the points A and H are 
fixed, the motion is conveyed to the small pilot valve E, thus 
giving 150 puffs a minute. The governor in shifting the point L 
brings the edge of the pilot valve nearer the port and so cuts off 
the steam earlier. 

The annular diameter or space between the rotor and the 
stator is gradually increased from inlet to exhaust, the blades 
being made longer in each ring. When the mechanical limit is 
reached, the diameter of the rotor is increased as at I and D so 
as to keep the length of blade within bounds. 

Balance pistons as at B, C, F are attached to the rotor, their 
office being to oppose end thrust upon those blades in corre- 
sponding diameter of the rotor. Communication is established 
through the passage V and pipe M between the eduction pipe 
and the back of these pistons, thus increasing the efficiency of 
their balancing and also taking care of any leakage past them. 

A small thrust bearing T prevents end play of the rotor, and 
is adjustable to maintain the proper clearance between the rings 
of blades; this varies from y % " at the admission to 1" at the 
exhaust. This bearing also takes up any extra unbalanced thrust. 
A turbine should operate with a high vacuum because without 
this it does not compare favorably with ordinary reciprocating 
engine from the point of economy. A usual method of securing 
the desired result is by forming a well in the lower part of the 
surface condenser, from which the water is drawn and delivered 
to the hot well by an independent pump. 

Separate pumps are provided to create the vacuum, these really 
being reversed air compressors, sometimes in two stages, which 
deal with the air alone. 

Where the ordinary type of vertical air pump is employed a 
booster or vacuum increaser is added, as nothing below 26" is 
admissible, 28" and 29" being always striven for. It is also 



PRACTICAL ENGINEERING 193 

preferable to use a certain amount of superheat with steam tur- 
bines, wet steam placing them at a disadvantage. 

To assist in producing the high vacuum, exhaust passages are 
made large, the eduction passage E in fig. 86 being nearly 
twenty-three times the area of the steam pipe. 

Among other details, a noteworthy feature is a small oil pump 
K, which circulates oil through bearings of the machinery, the 
oil being drawn from the tank under the governor shaft and 
gravitating there after use. No pressure of oil is employed. 
Stuffing rings prevent leakage ; these consist of alternate grooves 
and collars in shaft and bearing, like the grooves in an indicator 
piston. 

Ones. Why is a high vacuum desirable? 

Ans. Because the turbine is capable of expanding 
the steam to a very low terminal pressure, and this is 
necessary for economy. 

Ques. What may be said of the working 
pressures for turbines? 

Ans. To meet the varied conditions of service, 
turbines are designed to operate with: 1, high pres- 
sure, 2, low pressure, or 3, mixed pressure. 

High pressure turbines operate at about the same initial 
pressure as triple expansion engines. 

Low pressure, as here applied, means the exhaust pressure of 
the reciprocating engine from which the exhaust steam passes 
through the turbine before entering the condenser. 

Mixed pressure implies that the exhaust steam is supple- 
mented, for heavy loads, by the admission of live steam. 



194 AUDELS ANSWERS ON 



Ques. What determines the working pres- 
sure? 

Ans. When all the power is furnished by the 
turbine, it is designed for high pressure; when 
operated in combination with a reciprocating engine, 
low pressure is used for constant load, and mixed 
pressure for variable load. 



The De Laval steam turbine is termed by its builders a high 
speed rotary steam engine. It has but a single wheel, fitted with 
vanes or buckets of such curvature as has been found to be best 
adapted for receiving the impulse of the steam-jet. There are 
no stationary or guide blades, the angular position of the nozzles 
giving direction to the jet. The nozzles are placed at an angle of 
20 degrees to the plane of motion of the buckets. The best energy 
in the steam is practically devoted to the production of velocity 
in the expanding or divergent nozzle, and the velocity thus at- 
tained by the issuing jet of steam is about 4,000 feet per second. 
To attain the maximum of efficiency, the buckets attached to the 
periphery of the wheel against which this jet impinges should have 
a speed of about 1,900 feet per second, but, owing to the difficulty 
of producing a material for the wheel strong enough to withstand 
the strains induced by such a high speed, it has been found neces- 
sary to limit the peripheral speed to 1,200 or 1,300 feet per 
second. 

It is well known that in a correctly designed nozzle the adia- 
batic expansion of the steam from maximum to minimum pres- 
sure will convert the entire static energy of the steam into kinetic 
energy. Theoretically this is what occurs in the De Laval 
nozzle. The expanding steam acquires great velocity, and the 
energy of the jet of steam issuing from the nozzle is equal to 
the amount of energy that would be developed if an equal volume 



PRACTICAL ENGINEERING 



195 



of steam were allowed to adiabatically expand behind the piston 
of a reciprocating engine, a condition, however, which for 
obvious reasons has never yet been attained in practice with 
the reciprocating engine. But with the divergent nozzle the 
conditions are different. 




Fig. 88.— The Curtis turbine. 



The Curtis turbine is built by the General Electric Company 
at their works in Schenectady, N. Y., and Lynn, Mass. The 
larger sizes are of the vertical type, and those of small capacity 
are horizontal. In the vertical type the revolving parts are set 
upon a vertical shaft, the diameter of the shaft corresponding 
to the size of the machine. The shaft is supported by and runs 
upon a step bearing at the bottom. This step bearing consists 
of two cylindrical cast iron plates bearing upon each other and 
having a central recess between them into which lubricating oil 
is forced uuder pressure by a steam or electrically driven pump, 
the oil passing up from beneath. A weighted accumulator is 
sometimes installed in connection with the oil pipe as a convenient 
device for governing the step bearing pumps, and also as a safety 
device in case the pumps should fail, but it is seldom required 



196 AUDELS ANSWERS ON 

for the latter purpose, as the step bearing pumps have proven 
after a long service in a number of cases, to be reliable. The 
vertical shaft is also held in place and kept steady by three sleeve 
bearings, one just above the step, one between the turbine and 
generator, and the other near the top. These guide bearings are 
lubricated by a' standard gravity feed system. It is apparent 
that the amount of friction in the machine is very small, and as 
there is no end thrust caused by the action of the steam, the 
relation between the revolving and stationary blades may be 
maintained accurately. As a consequence, therefore, the clear- 
ances are reduced to the minimum. The Curtis turbine is 
divided into two or more stages, and each stage has one, two or 
more sets of revolving blades bolted upon the peripheries of 
wheels keyed to the shaft. There are also the corresponding 
sets of stationary blades, bolted to the inner walls of the cylinder 
or casing. 

The governing of speed is accomplished in the first set of 
nozzles, and the control of the admission valves here is effected 
by means of a centrifugal governor attached to the top end of 
the shaft. This governor, by a very slight movement, imparts 
motion to levers, which in turn work the valve mechanism. The 
admission of steam to the nozzles is controlled by piston valves 
which are actuated by steam from small pilot valves which are 
in turn under the control of the governor. Speed regulation is 
effected by varying the number of nozzles in flow, that is, for 
light loads fewer nozzles are open and a smaller volume of steam 
is admitted to the turbine wheel, but the steam that is admitted 
impinges against the moving blades with the same velocity always, 
no matter whether the volume be large or small. With a full 
load and all .the nozzle sections in flow, the steam passes to the 
wheel in a broad belt and steady flow. 



PRACTICAL ENGINEERING 197 



OUTLINE OF 
REFRIGERATION 



Refrigeration may be denned as the process of 
lowering the temperature of a body or of keeping the 
temperature below that of the atmosphere. Low 
temperature may be produced by : 

1. A transfer of heat from a warm to a cold body; 

2. By expansion of a gas; 

If work be done by the gas, as in pushing a piston, this 
work must be performed at the expense of the energy con- 
tained in the gas; the temperature of the gas will there- 
fore fall. 

3. Evaporation of liquids having low boiling points. 

When a liquid is changed to a vapor, a certain quantity 
of heat, called the latent heat of evaporation, must be add:d 
to the liquid to effect the change. When evaporation of 
a liquid takes place in the presence of other bodies, the 
heat required for it is drawn from these bodies, and they 
are thereby cooled. 



198 



AUDELS ANSWERS ON 



Ques. What may be said of mechanical 
refrigeration? 

Ans. Mechanical refrigeration is produced by ex- 
panding a heat medium from an ordinary temperature 
to a low temperature. 



Ammoniil jhCondenaerC 





Fig. 89. — Diagram showing the essentials of a mechanical compression system 
with vertical compressor. The condenser shown is of the atmospheric type, 
and the brine circulating system is used, the brine being cooled by the 
expansion coils in a tank and then circulated through pipes in the refrigerat- 
ing rooms. * 



Ques. What determines the choice of the 
heat medium? 

Ans. Its willingness to surrender its heat energy to 
surrounding objects; vapors are best employed. 



PRACTICAL ENGINEERING 199 

Ques. How is the vapor treated? 

Ans. It is compressed and then relieved of its heat 
in order to diminish its volume. It is then expanded 
so as to do mechanical work and its temperature is 
lowered. The absorption of heat at this stage by the 
vapor in resuming its original condition constitutes 
the refrigerating effect. 

Ques. What substances are used for refrige- 
ration? 

Ans. The most commonly employed agents are 
ammonia, carbonic acid, sulphur dioxide, and com- 
pressed air, the first named being the most generally 
used and approved, while the others have advantages 
for use on shipboard and in other places where the 
fumes of ammonia would prove objectionable. 

Ques. What are the advantages of ammonia ? 

Ans. It liquefies at low pressure, it is not explosive 
or inflammable, and possesses great heat absorbing 
power. 

Ques. Name two methods of refrigeration 
extensively used? 

Ans. The ammonia compression system, and the 
ammonia absorption system. 

Ques. Describe the ammonia compression 
system? 

Ans. The ammonia vapor is compressed to about 



200 



AUDELS ANSWERS ON 




PRACTICAL ENGINEERING 



201 



150 lbs. pressure, and is then allowed to flow into a 
cooler or surface condenser, where the heat due to the 
work of compression is withdrawn by the circulating 
water and the vapor is condensed to a liquid. It is then 
allowed to pass through an expansion cock and to ex- 
pand in the piping, thereby withdrawing heat from the 
1 'brine' ' with which the pipes are surrounded. This brine 




(Wasto Cooling yVatet 



Fig. 91. — Diagram of absorption system with vertical generator, weak liquor 
cooler, and brine tank. 



is then circulated by pumps through coils of piping and 
produces the refrigerating effect. The expanded 
ammonia gas is then drawn into the compressor under 
a suction of from 5 to 20 lbs., thus completing the 
cycle of operations. The brine consists of a solution 
of salt in water. Liverpool salt solution weighing 73 
lbs. per cu. ft. (sp. g. = 1.17) will not congeal at 0° F. 




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PRACTICAL ENGINEERING 203 

American salt brines of the same proportions congeal 
at 20° F. Ammonia required = 0.3 lb. per foot of 
piping. Leakage and waste amount to about 2 lb. 
per year per daily ice capacity of one ton. The brine 
should be about 6° colder than the space it cools. 

Ques. Describe the ammonia absorption 
system? 

Ans. In this system the compressor is replaced by 
a vessel, called the absorber, where the expanded 
vapor takes advantage of the property of water or a 
weak ammoniacal liquor to dissolve ammonia gas. 
(At 59° F. water absorbs 727 times its own volume 
of ammonia vapor.) The liquor in the absorber is 
then pumped into a still heated by steam pipes, where 
the ammonia gas is vaporized, the remainder of the 
process being then the same as in the compression 
system. The absorption system is less expensive to 
install, and commercial ammonia hydrate (62% water, 
sp. g. = 0.88) may be used in the absorber. 

Ques. Name two methods of compressing? 

Ans. Dry compression and wet compression. 

Ques. What is dry compression? 

Ans. Compression in a cylinder cooled by a water 
jacket. 

Ques. What is wet compression? 

Ans. In this method, the cylinder is not jacketed, 
but a certain amount of liquid anhydrous ammonia is 



204 AUDELS ANSWERS ON 

allowed to enter the cylinder with each stroke, the 
cylinder walls being cooled by its evaporation. 

The wet system is harder on packing, as there are few soft 
packings that will stand the freezing action of the liquid air- 
hydrous ammonia without becoming hard and causing leaky 
stuffing boxes. 



PRACTICAL ENGINEERING 205 

PRACTICAL 
ELECTRICITY 



Introductory. — Usually when a power plant in- 
cludes both steam engines and electrical generators, 
all are under the charge of one head. Such installa- 
tions being very numerous, the stationary engineer 
can no longer afford to be deficient in a knowledge of 
electricity, and especially so, since the examination 
for the higher grades of steam engineer's license 
includes questions on this subject. 

Electricity. — The name electricity is applied to an 
invisible agent known only by the effects which it 
produces, and the various ways in which it manifests 
itself. 

Electrical currents are said to flow through conductors. These 
offer more or less resistance to the flow, depending on the material. 
Copper wire is generally used as it offers little resistance. It is 
now thought that the flow takes place along the surface and not 
through the metal. 

The current must have pressure to overcome the resistance 
of the conductor and flow along its surface. This pressure is 



206 AUDELS ANSWERS ON 

called voltage caused by what is known as difference of potential 
between the source and terminal. 

An electric current has often been compared to water flowing 
through a pipe. The pressure uuder which the current flows 
is measured in volts and the quantity that passes in amperes. 
The resistance with which the current meets in flowing along 
the conductor is measured in ohms. 

The flow of the current is proportional to the voltage and 
inversely proportional to the resistance. The latter depends 
upon the material, length and diameter of the conductor. 

Since the current will always flow along the path of least re- 
sistance it must be so guarded that there will be no leakage. 
Hence to prevent leakage, wires are insulated, that is, covered 
by wrapping them with cotton, silk thread, or other insulating 
material. If the insulation be not effective, the current may 
leak, and so return to the source without doing its work. This 
is known as a short circuit. 

The conductor which receives the current from the source is 
called the lead, and the one by which it flows back, the return. 
When wires are used for both lead and return, it is called a 
metallic circuit; when the ground is used for the return, it is 
called a grounded circuit. 

An electric current is said to be : 

1. Direct, when it is of unvarying direction; 

2. Alternating, when it flows rapidly to and fro in 
opposite directions; 

3. Primary, when it comes direcrly from the source; 

4. Secondary, when the voltage and amperage of a 
primary current have been changed by a trans- 
former, or induction coil. 



PRACTICAL ENGINEERING 



207 



A current is spoken of as low tension, or high tension, accord- 
ing as the voltage is low or high. A high tension current is capable 
of forcing its way against considerable resistance, whereas, a low 
tension current must have its path made easy. A continuous 
metal path is an easy one, but an interruption in the metal, is 
difficult to bridge, because air is a very poor conductor. 

Air is such a poor conductor that it is usually, though erro- 
neously, spoken of as a "non-conductor;" it is properly called 
an insulator. 




Figs. 93 and 94. — Simple bar magnet and horse shoe magnet with keeper. 
These are known as permanent magnets as distinguished from electro 
magnets. The horse shoe magnet will attract more than the bar magnet 
because both poles act together. A piece of soft iron, or keeper, is placed 
across the ends of a horse shoe magnet to assist in preventing the loss of 
magnetism. 



Magnetism. — The ancients applied the word 
" magnet," magnes lapes, to certain hard black stones 
which possess the property of attracting small pieces 
of iron, and as discovered later, to have the still more 
remarkable property of pointing north and south 
when hung up by a string; at this time the magnet 
received the name lodestone. 



208 



AUDELS ANSWERS ON 



Magnets have two opposite kinds of magnetism or magnetic 
poles, which attract or repel each other in much the same way 
as would two opposite kinds of electrification. 

One of these kinds of magnetism has a tendency to move 
toward the north and the other, toward the south. The two 



s s 




Fig. 95. — Diagram of a vibrator coil. The parts are as follows: A, contact 
screw; B, battery; C, core; D, vibrator terminal; G, condenser; P, pri- 
mary winding; S, secondary winding; W, switch; Y, vibrator. When the 
switch is closed, the following cycle of actions takes place: a, the primary 
current flows and magnetizes core; b, magnetized core attracts the vibrator 
and breaks primary circuit; c, the magnetism vanishes, inducing a momen- 
tary high tension current in the secondary winding; d, magnetic attraction 
of the core having ceased, vibrator spring re-establishes contact; e, primary 
circuit is again completed and the cycle begins anew. 



regions, in which the magnetic property is strongest, are called 
the poles. In a long shaped magnet it resides in the ends, 
while all around the magnet half way between the poles there 
is no attraction at all. 

The poles of a magnet are usually spoken of as north pole and 
south pole. 



PRACTICAL ENGINEERING 209 

When a current of electricity passes through a wire, a certain 
change is produced in the surrounding space producing what is 
known as a magnetic field. If the wire be insulated with a cover- 
ing and coiled around a soft iron rod, it becomes an electro- 
magnet having a north and south pole, so long as the current con- 
tinues to flow. The magnetic strength increases with the number 
of turns of the coil, for each turn adds its magnetic field to that 
of the other turns. 

Induction. — If a second coil of wire be wound 
around the coil of an electro-magnet, but not touching 
it, an induced current is produced in this second coil 
by what is known as induction, each time the current 
in the inside coil begins or ceases flowing. The inside 
coil is called the primary winding and the outside coil 
the secondary winding. Similarly, the current passing 
through the inside coil is called the primary current 
and that in the outside coil the secondary or induced 
current. 

It has been found that by varying the ratio of the number of 
turns in the two coils the tension or voltage of the two currents 
is changed proportionately. That is, if the primary winding be 
composed of ten turns and the secondary of one hundred, the 
voltage of the secondary current is increased ten times that of the 
primary. This principle is employed in the construction of in- 
duction coils and transformers. 

Ques. What is a volt? 

Ans. An electromotive force or pressure which 
will produce a current of one ampere in a circuit 
having a resistance of one ohm. 



210 



AUDELS ANSWERS ON 



Ques. What is an ohm? 

Ans. The resistance offered to an electric current 
by a column of mercury one square millimeter in sec- 
tion and 106 centimeters long, at a temperature of 
0° C. 




Figs. 96 and 97. — Illustrating the construction of volt and ammeters. The 
soft iron needle, a, is pivoted within a coil of very fine wire, b, and held 
normally out of line with the axis of the coil by means of a permanent 
magnet, M, or a weight, w. Passing a current through the coil, b, causes 
magnetic lines to flow (vertically in the illustrations) through its center, 
and these tend to pull the needle around into line with them. The perma- 
nent magnet, M, or the weight, w, resists this pull, and the distance that 
the needle is deflected indicates the strength of the current in the coil. 
A pointer, e, is attached to the needle, a, and the scale,/, is marked in volts; 
the pointer, e, indicates on the scale the voltage at the terminals, c, d, of the 
coil, b. 



Ques. What is an ampere? 

Ans. The current produced by an electromotive 
force of one volt in a circuit having a resistance of one 
ohm. 

An ampere is that quantity of current which will deposit 
.001118 gramme of silver per second. 



PRACTICAL ENGINEERING 211 

Ques. State Ohm's Law, and the formulae 
derived from it? 

Ans. Considering a steady flow of electricity in a 
given circuit, then according to Ohm's law: the amount 
of current in amperes is equal to the electromotive force in 
volts divided by the resistance in ohms. 

The law may be expressed in three simple formulae, when I is 
used as the symbol of the current strength in amperes, R, as that 
of the resistance in ohms, and E, the electromotive force in 
volts, as follows: 

R' 

which reads: The current in amperes equals the electromotive 
force in volts divided by the resistance in ohms. 

E = IR, 
which reads: The electromotive force in volts equals the current 
in amperes multiplied by the resistance in ohms. 

which reads: The resistance in ohms equals the electromotive 
force in volts divided by the current in amperes. 

Ques. What is a watt? 

Ans. The product of one ampere multiplied by 
one volt. 

Ques. What is the electrical horse power? 

Ans. The unit of electrical work, being the 
mechanical horse power expressed in watts. It is 
equal to 746 watts. 



212 AUDELS ANSWERS ON 

Ones. What is meant by the carrying capac- 
ity of a wire? 

Ans. The amount of current it will carry without 
heating to such an extent as to cause danger of burning 
the insulation or wood work. 




Fig. 98. — Recording watt hour meter. It consists of a very small motor 
which drives a delicate train of gears, the hands of which indicate on dials 
the number of watt hours supplied. The two coils of wire enclose the 
armature and furnish the field magnetism. The fan blades on the lower 
part of the shaft serve as a brake to steady the rotation of the shaft. 
There are several forms of motor meter, all based on the same principle — 
that of making the speed of the motor proportional to the watts supplied to 
the circuit. 

Ques. What is meant by the " drop " in a 
circuit? 

Ans. The drop in a circuit means the number of 
volts lost in overcoming the resistance of the circuit. 



PRACTICAL ENGINEERING 213 

It corresponds to the drop in pressure along a steam 
pipe or water main. 

TABLE OF CURRENT CAPACITY OF WIRES. 



No. of wire, 


Rubber covered 


Weather proof 


B. & S. gage. 


Wire. 


Wire. 




Amperes. 


Amperes. 


18 


3 


5 


16 


6 


8 


14 


12 


16 


12 


17 


23 


10 


24 


32 


8 


33 


40 


6 


46 


64 


5 


54 


77 


4 


65 


92 


3 


76 


110 


2 


90 


131 


1 


107 


156 





129 


185 


00 


150 


220 


000 


177 


262 


0000 


210 


312 



Ques. Describe a dynamo. 

Ans. A dynamo consists of three essential parts, a 
field magnet, an armature, and a commutator. The 
field magnet must be magnetized either by the dynamo 
itself or some outside source. The armature consists 
of coils of insulated copper wire wound upon a core of 
thin iron discs which is mounted on a shaft and caused 



214 



AUDELS ANSWERS ON 



to rotate between the poles of the field magnet in 
such a manner that the lines of magnetic force passing 
through the coils of the armature are constantly 
increasing or decreasing. This action causes alter- 
nating currents of electricity to be generated in the 
coils of the armature, which are collected by suitable 
brushes at the commutator and converted into direct 
current for the external circuit. 




Pig. 99. — A four pole dynamo, mounted on V rails with adjustment for tight- 
ening the belt. 

Ques. What is meant by the magnetic cur- 
rent? 

Ans. The path through which the magnetic lines 
or force travel. 



PRACTICAL ENGINEERING 215 

Que*s. What is the object of making the 
armature core of thin discs rather than of solid 
metal ? 

Ans. To prevent eddy currents which convert 
energy into heat; this would not only produce a 
waste of energy, but would also injure and perhaps 
destroy the insulation of the armature coils. 

Ques. How are dynamos classified according 
to the winding of their field magnets? 

Ans. Into three classes: series, shunt, and com- 
pound dynamos. 

Ques. What is a series dynamo? 

Ans. A dynamo in which all the current produced 
by the machine flows through its field magnet coils. 

This is accomplished by taking a wire from one brush, carry- 
ing it the required number of times around the field magnet and 
then connecting it to the external circuit; the other end of the 
external circuit is connected to the other brush. 

Ques. What is a shunt dynamo? 

Ans. One in which only a portion of the total 
current of the machine passes through the field magnet 
coils. 

Ques. What is a compound dynamo? 

Ans. A dynamo having two windings: a series 
winding, around which the main current flows; and 



216 



AUDELS ANSWERS ON 



a shunt winding, through which a fraction of the 
main current flows. 

Ques. For what class of work is a shunt 
dynamo used? 

Ans. For work requiring a constant pressure at 
all loads. 




Fig. 100. — Series dynamo connections; also called constant current machine 
because the voltage rises with the load. This type of machine requires a 
regulator which is usually an electro-mechanical device for shifting the 
brushes to conform with the load. M M, field coils ; B B, brushes; C, 
commutator; L, lamp. The field coils consist of a few turns of heavy 
wire joined in series with the armature so that the whole current passes 
through the coils to the external circuit, thus maintaining the field; the 
strength of field increases with the load. 

Ques. Does a shunt machine maintain a 
constant pressure at all loads? 

Ans. Nearly so; the pressure falls off a little as 
the load increases. 



PRACTICAL ENGINEERING 



217 



Ques. What system of distribution requires 
a constant pressure at all loads? 

Ans. The ordinary parallel or multiple system used 
for the lighting of buildings. 

Ques. Are shunt dynamos used in general 
for this class of work? 

Ans. No; they have been superseded largely by 
the compound dynamo, which gives a closer regula- 
tion of pressure. 




Fig. 101. — Shunt dynamo. Generally used for incandescent lamps and motors. 
M M, field coils; B B, brushes; C, commutator; L, lamp circuit; R, field 
rheostat. The field coils consist of many turns of fine wire connected in 
parallel to the external current, thus obtaining a small portion of the arma- 
ture current for maintaining the field. The voltage is regulated by adding 
or cutting out resistance in the field by means of the rheostat R. 

Ques. What is meant by an overcompounded 
dynamo? 

Ans. One which automatically raises the pressure 
a little in proportion as the load increases, due to 
increasing the series winding. 



218 



AUDELS ANSWERS ON 



Ques. What are its advantages over one that 
would maintain the pressure constant? 

Ans. Such a dynamo would make up for a slight 
fall in the speed of an engine, which takes place as 
the load increases; it also makes up for a loss in 
pressure on the circuit wires, which loss is proportional 
to the load which they carry. 




Pig. 102. — Compound wound dynamo. This has two windings on the field 
magnets, and is a combination of the series and the shunt dynamos. 5 S, 
series winding; F F, shunt winding; R, shunt rheostat; C, commutator; 
L, external circuit; D, series cut out switch, which permits dynamo to 
be used as simple shunt machine. The series coils strengthen the field as 
the load rises, and by varying the number of series turns, different results 
may be obtained. If the series coils be of many turns, the field magnets 
will be so strengthened as to cause the voltage to rise with increase of load. 
This is called over compounding. 

Ques. How is overcompounding actually 
obtained? 

Ans. By increasing the number of turns in the 
series coil of a compound dynamo above what would 
be necessary to give a constant pressure machine. 



PRACTICAL ENGINEERING 219 

Ques. Can the pressure furnished by a shunt 
or compound dynamo be varied? and if so, how? 

Ans. Yes; it could be varied by altering the speed 
of the engine, but the common method is to insert an 
adjustable resistance called a " rheostat " in series 
with the shunt field coils. When the arm of the 
rheostat is turned one way more resistance is thrown 
into the shunt circuit, which cuts down the current 
flowing around the coils. As this diminishes the 
strength of the field magnet the pressure furnished 
by the machine is lessened. Moving the rheostat arm 
in the other direction cuts out resistance and raises 
the pressure. 

Ques. What care must be given to a dynamo 
in order to make it run properly? 

Ans. It must be kept clean and dry. The bear- 
ings, of course, need no more nor no less attention 
than similar bearings in other machinery. The parts 
which require the most care are the commrtator and 
brushes. 

Ques. What causes " sparking " at the 
brushes? 

Ans. The causes for " sparking " are varied and 
many; it may be due to the following among other 
causes: 1, The brushes may not be set at point of 
commutation; 2, brushes may be wedged in holders; 
3, brushes may not be properly fitted to commutator; 



220 AUDELS ANSWERS ON 

4, brushes may not bear with sufficient pressure; 

5, brushes may be burned on ends; 6, commutator 
may be rough; 7, commutator may have a loose or 
projecting bar; 8, commutator may be dirty, oily or 
worn; 9, machine may be badly designed or over- 
loaded; 10, loose connection of coil to commutator, 
or open circuit. 

Ques. State in a general way how a dynamo 
should be connected to switch board, how cir- 
cuits should be run from same, and where 
circuit breakers and fuses should be placed, 
explaining why the latter are put in. 

Ans The exact arrangement of the switch board 
varies with the judgment of the designer, and the 
requirements of the case. Dynamos are generally 
connected from the terminal board to the switch 
board by cables. Generally the positive lead is 
connected to one leg of the switch. The circuit 
switches are connected to the main switch by means, 
of bus bars which take the entire current from the 
main switch and distribute it to the different circuit 
switches. Fuses and circuit breakers are used to 
protect the lines and machines from burning out, due 
to excessive current caused by* short circuits or an 
overload, either momentary or sustained. They are 
generally placed between the dynamo and main 
switch; fuses are placed on all distributing circuits 
between the line and the switch. 



PRACTICAL ENGINEERING 



221 



Ques. What is an automatic circuit breaker? 
Upon what does its action depend, and what 
advantage has it over a fuse? 

Ans. An automatic circuit breaker is an apparatus 
for opening the circuit when an excessive amount of 
current passes through it. A common form depends 
for its action upon the principle that a bar of iron 
will tend to balance itself in a solenoid. In this case 




Fig. 103. — Single pole circuit breaker (shown in off position). The laminated 
switch contact bridge C, when on, interconnects the two fixed contact 
plates, K, K: and the auxiliary carbon contacts CC break the circuit after 
the metal contacts C and K, K have separated, thus lessening the spark wear 
at the latter. The "breaker" is closed by hand, and is opened electromag- 
netically when the current exceeds a predetermined strength. It may also 
be released by hand when necessary. Included in the main circuit between 
the terminals is a solenoid. When the breaker is put on, it is held in place 
by a catch, and if the current become too great, the solenoid acts with 
such force on its armature that the latter — through simple connecting 
mechanism — "trips" the catch, and allows the switch part to be pulled off by 
the helical spring S. The solenoid, etc., are contained in the box B, and 
the thumb nut at N enables the apparatus to be adjusted within 
certain limits. 



222 AUDELS ANSWERS ON 

the solenoid is composed of three or four turns of the 
entire current conductor; as the current increases 
the soft iron bar raises until it trips the spring actu- 
ated switch. Their advantage over a fuse is, that in 
case of a momentary overload they can be quickly 
thrown in again, whereas a fuse takes time to replace 
and, under certain conditions, is a dangerous opera- 
tion. 

Ques. What style winding is best adapted 
for a motor which is to run at a constant speed 
and carry a variable load? 

Ans. The shunt winding is almost universally 
used for motors with variable load and using direct 
current. This type of motor gives a very nearly 
constant speed with a variable load, providing the 
voltage be kept constant. 

Ones. What is a starting box, and why is 
one required in connection with a motor? 
Explain also the automatic cut out and the 
reasons for attaching same? 

Ans. A starting box is necessary in order to insert 
a resistance in the circuit, so that the current may 
be turned on gradually, otherwise one or more coils 
would burn out, as the total current would pass 
through them before the armature had a chance to 
start revolving. An automatic cut out is so arranged 



PRACTICAL ENGINEERING 223 

that should the external circuit be broken, the box 
will automatically cut in its resistance and then open 
the armature circuit. 

Ques. Should motors be run on indepen- 
dent circuits? Why? 

Ans. Motors should be run on independent cir- 
cuits, very often, however, they are cut in almost 
anywhere. The work of a motor with a variable 
load requires more or less current and if not on a 
separate circuit, unless the conductors are excessively 
large, will make the lights unsteady. 

Ques. What general rules should be observed 
in making electrical connections? 

Ans. The metallic surfaces should be perfectly 
clean and make good contact. They should also be 
mechanically strong enough to withstand any strain 
likely to be encountered. 

Ques. What broad rule should be observed 
on the score of personal safety when handling 
electrical conductors? 

Ans. Be careful not to interpose any portion of 
the body where such will become a conductor of 
current. 

A good rule for personal safety when working around elec- 
trical machines is to wear rubber gloves; use one hand only, as 
much as possible, and always stand on a dry or insulated spot. 



224 



AUDELS ANSWERS ON 



Ques. What is a simple primary cell ? 

Ans. A combination of two dissimilar metal plates 
in an exciting fluid or electrolyte contained in a glass jar. 




Fig. 104. — A primary cell. Volta discovered that an electromotive force may 
be created between two dissimilar substances through chemical action set 
up by a so.ution in which they are immersed. This discovery led to the 
construction of the primary cell, long known as the voltaic cell. The cell 
consists essentially of two plates of different substances standing apart in a 
jar containing a solution which attacks one and not the other. By joining 
the outside terminals of the plates by a conducting wire, a current will flow 
from one to the other so long as the chemical action or electrolysis continues 
through the solution. The solution is known as the electrolyte, and the two 
plates are called the elements. This type of cell is called primary to dis- 
tinguish it from the secondary or storage cell. 

Ques. What is a " battery? " 

Ans. A word often used incorrectly for a cell; it is 
a combination of two or more cells joined together so 
as to form one unit. 



PRACTICAL ENGINEERING 225 

Ques. What is a " secondary " or " storage " 
cell? 

Ans. One in which electrical energy may be 
stored. 

Ones. Describe a secondary cell? 

Ans. As usually constructed, it consists of a posi- 
tive and negative set of lead plates immersed in an 
electrolyte of dilute sulphuric acid. The proportion 
of acid to water is about one part acid to three and 
one-half parts of water. 

In making the electrolyte, the acid should be added to the 
water — never the reverse. 

Ques. Explain how a storage cell works. 

Ans. In passing an electric current through a cell 
the plates undergo a chemical change; when this is 
complete the cell is said to be charged. A quantity of 
electricity has been stored in the cell, hence the name, 
storage cell. The cell after being charged will deliver 
a current in a reverse direction because during the 
discharge a reverse chemical action takes place which 
causes the plates to resume their original condition 
When fully charged the positive plates are coated 
with peroxide of lead and are brown in color and the 
negative plates gray. 

Ques. Describe the method of charging. 

Ans. In charging, a direct current should be used — 
never an alternating one, care being taken to connect 



226 



AUDELS ANSWERS ON 



the positive wire to the positive terminal and the 
negative wire to the negative terminal. If con- 
nected in the reverse direction serious injury to the 
battery will result. The simplest method of charging 
is from an incandescent light circuit, using lamps 





Fig. 105. — The Exide storage cell. The positive and negative plates are sep- 
arated by thin sheets of perforated hard rubber, placed on both sides of 
each positive plate. The electrolyte and plates are contained in a hard 
rubber jar. 

Fig. 106. — An Exide battery of five cells. The box which holds the cells is 
usually made of oak, properly reinforced, with the wood treated to render 
it acid proof. The terminals, as shown, consist of metal castings attached 
to the side of the box and plainly marked. 



connected in parallel to reduce the voltage to that 
of the battery, the current being adjusted by varying 
the number of lamps in the circuit. A storage battery 
should be charged once every two months whether it 
be used or not. 



PRACTICAL ENGINEERING 227 

Ques. What is sulpha tion? 

Ans. The formation of sulphate of lead on the 
plates of a storage cell in the form of a very hard 
grayish coating. This sulphate of lead is practically 
an insulator, hence, plates so affected are rendered 
useless unless it be removed. 

Ques. Name some causes of sulphation. 

Ans. Too strong or too hot electrolyte, over dis- 
charging, etc. The most common cause of sulphation 
is over discharging. A battery that is discharged to a 
low point and then allowed to lie around unused for a 
considerable time will be destroyed by sulphation or 
rendered practically useless. 

Ques. What may be said of local sulphation? 

Ans. Local sulphation is caused by small particles 
of the active materials, which have become dislodged 
from the plates, catching in the separators. The latter 
are used to prevent the plates touching and. forming 
a " bridge " between two plates and discharging 
them entirely. 

Sediment, which gradually accumulates in the bottom of the 
jars, should be removed before it reaches the bottom of the 
plates. 

Ques. How should sulphated plates be 
treated ? 

Ans. When the plates are sulphated the battery 
should be given a long slow charge at one-quarter 



228 AUDELS ANSWERS ON 

the normal charging rate, till the electrolyte shows 
the proper specific gravity and the voltage has 
attained its maximum. The terminals and top of the 
cell should be kept free from acid, which will cause 
corrosion. 

Ques. What is the proper specific gravity 
for the electrolyte? 

Ans. The specific gravity of the electrolyte at the 
end of the charge should be 1.3. The specific gravity 
should not be altered when the battery is fully 
charged. 

Ones. Describe the Edison three wire system. 

Ans. The Edison three wire system is a peculiar 
combination of series and multiple systems. Two 
lamps are placed in series with each other and the 
sets of two are in multiple with each other. A con- 
ductor, called the neutral, connects the point of junc- 
tion of the lamps which are placed in series with each 
other and runs to the point of junction of the two 
generators (in series with each other) which supply 
the system. 

Ques. What is the advantage of the Edison 
system? 

Ans. It secures economy in the size of wire, from 
the fact that it permits the distribution at a higher 
pressure without any very serious disadvantages ; for 
example, the distribution on the feeders and mains is 



PRACTICAL ENGINEERING 229 

essentially at 220 volts, while the pressure on the 
branch circuits and the lamps is only 110 volts. 

Ques. What is a dynamotor? 

Ans. A combination of dynamo and motor on the 
same shaft, one receiving current and the other de- 
livering current, usually of different voltage, the 
motor being employed to drive the dynamo with a 
pressure either higher or lower than that received at 
the motor terminals. In one form two armatures are 
mounted on one shaft in a single field or in separate 
fields ; one is a motor armature driven by the original 
current; the other generates new current. This is a 
" motor-dynamo," and it can transform continuous 
current up or down. Another form of dynamotor 
is called the continuous alternating transformer. This 
is arranged so as to change a continuous into an alter- 
nating current or the reverse. 

Ques. What is a fuse, and why and where 
is it used? 

Ans. A fuse consists of a piece of metal, usually 
some alloy of lead which will melt at a fairly low 
temperature, soldered to copper terminals. It is 
intended to melt whenever the current passing 
through it exceeds the safe carrying capacity of the 
wire which the fuse is designed to protect. Fuses are 
placed at all points of a circuit where there is a change 
made in the size of the wires. 



230 



AUDELS ANSWERS ON 



Ques. What is an alternating current? 

Ans. A current which changes its direction many 
times each second. 




Fig. 107. — Application and construction of the sine curve. The sine curve is a 
wave like curve used to represent the changes in strength and direction of 
an alternating current. At the left of the figure, is shown an elementary 
alternator, consisting of a loop of wire A B C D, whose ends are attached 
to the ring and shaft F and G, being arranged to revolve in a uniform 
magnetic field indicated by the vertical arrows representing magnetic lines 
at equidistances. The alternating current induced in the loop is carried to 
the external circuit through the brushes M and S. The loop as shown, is in 
its horizontal position but at right angles to the magnetic field. The dotted 
circle indicates the circular path described by A B or C D during the revo- 
lution of the loop. Now, as the loop rotates the induced electromotive force 
will vary in such a manner that its intensity at any point of the rotation is 
proportional to the sine of the angle corresponding to that point. Hence, on the 
horizontal line which passes through the center of the dotted circle, take 
any length as 08, and divide into any number of equal parts representing 
fractions of a revolution, as 0°, 90°, 180°, etc. Erect perpendiculars at 
these points, and from the corresponding points on the dotted circle project 
lines parallel to 08; the intersection with the perpendicular give a point 
through 2 at the 90° point of its revolution, hence, projecting over to the 
corresponding perpendicular gives 2'2, whose length is proportional to the 
electromotive force at that point. In like manner other points are obtained, 
and the curved line through them will represent the variation in the electro- 
motive force for all points of the revolution. At 90° the electromotive force 
is at a maximum, hence by using a pressure scale such that the length of 
the perpendicular 2'2 for 90° will measure the maximum electromotive 
force, the length of the perpendicular at any other point will represent the 
actual pressure at that point. The curve lies above the horizontal axis 
during the first half of the revolution and below it during the second half, 
which indicates that the current flows in one direction for a half revolution 
and in the opposite direction during the remainder of the revolution. 



PRACTICAL ENGINEERING 231 

Ques. What is an alternation of the current? 

Ans. A rise from zero potential to a maximum 
potential and fall back to zero potential. 

Ques. Define the term " phase/ ' 

Ans. In wave, vibratory, and simple harmonic 
motion, the portion of one complete vibration, meas- 
ured either in angle or in time that any moving point 
has executed. 

Ones. What is a single phase alternating 
current ? 

Ans. A simple alternating current of uniform fre- 
quency as distinguished from polyphase currents. 

Ques. Describe a two phase alternating cur- 
rent. 

Ans. Two alternating currents of the same fre- 
quency, but having a difference in phase of a quarter of 
a period, a diphase or quarter phase alternating current. 

If two identical simple alternators have their armature shafts 
couples in such a manner, that when a given armature coil on 
one is directly under a field pole, the corresponding coil on the 
other is midway between two plates of its field, the two currents 
generated will differ in phase by a half alternation, and will be 
two phased currents; similarly, three phased currents could be 
generated by coupling the armatures of three simple alternators 
so that the corresponding coils on each are equally "staggered" 
with respect to each other. 

Two phase and three phase currents differ in this respect; 
the two phase system requires four wires to connect the gener- 
ators with the motors, and their action is that of two distinct 



232 AUDELS ANSWERS ON 



and separate circuits through which are passing simple alter- 
nating currents of electricity which act upon the revolving part of 
the motor like the two cranks' on a cross connected engine at right 
angles to each other, or one 90 degrees in advance of the other. 

Ques. What is a polyphase alternating cur- 
rent? 

Ans. One having more than one phase; two or 
more alternating currents which differ in phase in a 
fixed proportion. 

Ones. What is the advantage of the alter- 
nating current? 

Ans. It can be transformed from a large current 
at low voltage to a small current at high voltage, or 
vice versa. 

Ques. Of what advantage is this? 

Ans. It permits the transmission of large power 
to a great distance economically. The higher the 
voltage the less the current for a given amount of 
power, consequently, the smaller the line wire may 
be for a given loss, or the smaller the loss with a given 
size of wire. 

For example, 1,000 kilowatts at 2,000 volts demand a current 
of only 500 amperes; if the pressure were 500 volts, the current 
would be 2,000 amperes. Now, suppose there were a line that 
transmitted 500 amperes with a drop of 100 volts, or 5 per cent. 
The drop with 2,000 amperes would be 400 volts, or 80 per cent, 
of the available pressure of 500 volts. Hence, to transmit the 
1,000 kilowatts at 500 amperes with a loss of 5 per cent., the 
line would have to be sixteen times as heavy as it would with a 
pressure of 2,000 volts. 



PRACTICAL ENGINEERING 



233 



Ques. How is the voltage of an alternating 
current raised or lowered? 

Ans. By a transformer. 

Ones. Describe a transformer, 

Ans. It is an apparatus similar to an induction coil, 
and consists essentially, of two coils of insulated wire 




Fig. 108. — Transformer with case removed. It consists of an iron core of thin 
sheets, M, on which are wound two sets of coils called the primary and 
secondary windings. 



wound adjacently upon a soft iron core; the primary 
coil of high resistance, consisting of many turns of fine 
wire, is connected to the high voltage circuit, and the 
secondary coil, consisting of fewer turns of coarse wire, 
furnishes the current at a reduced pressure. 

This is a "step down" transformer; in a "step up" trans- 
former the conditions are reversed, that is, primary winding 



234 AUDELS ANSWERS ON 

is made up of a few turns of coarse wire and the secondary 
winding of many turns of fine wire. 

Ones. Cannot direct current be generated 
at high voltage? 

Ans. Yes, up to certain limits. Above 2,000 or 
3,000 volts, however, the commutator becomes pro- 
hibitively expensive, and it is extremely difficult to 
obtain smooth commutation at such high potentials. 
Moreover, the voltage is too high to use at the lamps 
or motors, and to reduce it, the use of a combined 
motor and dynamo is required, the motor winding 
being designed for the high potential and the dynamo 
winding for the lower distribution voltage. 

Ques. What is a rotary converter? 

Ans. A dynamo for generating both direct and 
alternating current. 

If conductors be led from the armature of a direct current 
machine to collector rings, alternating currents may be obtained; 
if the machine be run as a direct current motor alternating cur- 
rents may be had at the collector rings; and if run as a syn- 
chronous alternating current motor, direct current may be ob- 
tained from the commutator. 

Ques. What is an alternator? 

Ans. A generator of alternating current; it is 
essentially a dynamo with collector rings instead of a 
commutator. 



PRACTICAL ENGINEERING 235 

Ones. What else may be said of alternators? 

Ans. Alternators are classified with respect to the 
current, as: 1, Single phase; 2, two phase; or 3, 
polyphase; with respect to construction as: a, those 
with stationary field magnet and rotating armature; 
b, those with rotating field magnet and stationary 




Fig. 109. — An alternator. The field revolves and the armature is stationary. 
Alternators are always multipolar because a high frequency is desirable. 
With stationary armature, the armature wires can be more securely fastened 
and more effectually insulated. 



armature; c, those with both field magnet part and 
armature part stationary, but having revolving in- 
ductors made up of appropriate pieces of iron. Alter- 
nating current generators or alternators are usually 



236 AUDELS ANSWERS ON 



multipolar, having north and south poles alternating 
around the field. The number of changes of direction 
of the current per revolution is the same as. the num- 
ber of coils in the armature or poles in the field, the 
armature coils in simple current machines being equal 
in number to the poles. The field magnets are often 
excited by a separate generator. 



Fig. 110. — Alternator armature, showing details of coils, core and frame. 

Ques. What is the advantage of polyphase 
distribution? 

Ans. The ability to supply lamps and self-starting 
motors from the same circuit or from the same char- 
acter of generator, avoiding a multiplicity of generator 
types at the station. 



PRACTICAL ENGINEERING 237 

Ques. Cannot self-starting motors be oper- 
ated on simple alternating current lines? 

Ans. Yes; self -starting single phase motors are in 
use, but they do not give quite so satisfactory results 
as polyphase machines, especially in larger sizes. 
Moreover, they require special construction or auxil- 
iary apparatus to enable them to be self -starting. 
A simple single phase motor, without any special 
starting device, will not move from a dead rest when 
thrown into circuit. 

Ones. Are two phase and three phase motors 
self -star ting? 

Ans. Yes. 

Ones. Is there any preference between two 
phase and three phase systems? 

Ans. The three phase system is more economical 
in line wires, but the two phase system is easier to 
maintain in " balance," and consequently gives better 
regulation at the generators. 

Ques. Why is the three phase system more 
economical in wire? 

Ans. Because of the phase relations between the 
three currents. The three currents rise and fall at 
different instants; the result of this is that the 
" drop " in a three wire three phase line is exactly 
the same that it would be in a two phase line having 
four wires of the same size as those in the three phase 
line. 



238 



AUDELS ANSWERS ON 



Ques. How does it compare with a single 
phase line? 

Ans. Exactly the same way; the amount of 
copper required in a single phase two wire line is the 
same as that required in a two phase four wire line 
for the same load and drop ; the two wires have each 
twice the cross section of each of the four wires of the 
two phase line. Therefore, the three phase three wire 
line requires three-fourths the amount of copper for a 



HIGH PRESSURE MAINS 



HIGH PRESSURE MAINS 




Figs. Ill and 112. — Alternating circuit diagrams. High pressure currents are 
carried either from the central station to special sub stations (or transformer 
stations), from whence low pressure mains distribute the current to the 
houses, or the high pressure current enters each building in high pressure 
mains, and is transformed in the building by means of a transformer placed 
in the cellar or on the poles carrying the wires. 

Fig. 113. — Two phase alternating system with separate circuit for each phase. 



PRACTICAL ENGINEERING 



239 



given set of conditions that is required by the simple 
alternating current line with two wires, and also by 
the four wire two phase line. 










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Figs. 114 and 115. — Two and three phase circuits. In the two phase circuit, 
one wire may be saved by combining B and C, as shown in fig. 114. This 
arrangement is preferable for long distances, because of the saving in copper 
wire, but the chance of trouble increases. The wire B in such a case must 
have a cross section 41 per cent, greater than it would have otherwise. Fig. 
115 is the diagram of a three phase circuit with transformers, Ti, T 2 , T 3 . 

Ques. How are alternating current motors 
classified ? 

Ans. There are two general classes; synchronous 
and induction; each of these is again divided into 
single phase and polyphase. 



240 AUDELS ANSWERS ON 

Ques. What is the difference between syn- 
chronous and induction motors? 

Ans. A synchronous motor has its field excited 
from some direct current source, while its armature 
takes current from the alternating current line, 
whereas an induction motor field is supplied from 
the alternating current circuit and its armature is 
not connected to any source of current, the currents 
in it being induced by the field — hence its name of 
" induction " motor. 

A synchronous motor having a certain number of poles and 
being supplied with current from an alternator having the same 
number of poles will run at the same speed as that of the alter- 
nator, regardless of the load or voltage — hence the name "syn- 
chronous" motor; on the other hand, an induction motor, al- 
though tending to run in synchronism with the generator which 
supplied it with current, cannot do so, but lags behind the 
generator by a small amount, the actual lag, or "slip" as it is 
termed, varying with the load on the motor. 

Ques. What means is usually employed for 
starting synchronous motors? 

Ans. A small induction motor is mounted on the 
shaft or arranged to be belted to the synchronous 
motor shaft during the starting up period. The in- 
duction motor is thrown in circuit first, and brings 
the armature of the synchronous machine to a speed 
slightly above synchronism; then the synchronous 
armature is connected to the mains and the induction 
motor is cut out. The field magnet of the synchron- 
ous motor is fully excited beforehand. 



PRACTICAL ENGINEERING 241 

Ques. Is either type of motor anything like 
an alternator? 

Yes. A synchronous motor is precisely like an 
alternator. In fact, the two are interchangeable, 
exactly as in the case of dynamos and motors. 

Ones. What is a recording watt hour meter? 

Ans. A form of meter designed to register the watt 
hours expended during a perod of time. It is used to 
record the amount of electric power furnished to a 
consumer by a central station. 

It is usually made in the form of a very small motor which 
drives a delicate train of gears, the hands of which indicate on 
dials the number of watt hours supplied. Watt hour meters are 
made for both alternating and direct currents. 

Ques. What is meant by power factor? 

Ans. The ratio between the true watts and the 
apparent watts of an alternating current, or the pro- 
portion of the apparent watts that is available for 
power. 

In the direct current, the power, measured in watts, is the 
product of the volts and amperes in the circuit. In alternating 
current, this is only true when the current and electromotive 
force are in phase. If the current either lag or lead, the values 
shown on the voltmeter and ammeter will not be true simul- 
taneous values. The power in an alternating current circuit at 
any instant is the product of the simultaneous values of current 
and voltage. The volts and amperes indicated on the meters must 
be multiplied together and their product multiplied by the power 
factor before the true watts are obtained. 



242 AUDEL ANSWERS ON 

Ones. What is understood by the term kilo- 
volt ampere? 

Ans. Apparent power in alternating current circuits 
is expressed in kilovolt amperes when the real power 
is expressed in kilowatts. 



PRACTICAL ENGINEERING 243 



ELEVATORS 



Ques. What two classes of elevator are in 
general use? 

Ans. Electric and hydraulic. 

Ques. What is an overbalanced elevator? 

Ans. One having a counterweight heavier than the 
car. 

Ques. What is the advantage of overbalancing 
an elevator? 

Ans. It permits a smaller motor to be used. 

Ques. Into what two classes are safety devices 
divided ? 

Ans. Into motor safeties and car safeties. 

Ones. By what different means is the brake 
operated on electric elevators ? 

Ans. By mechanical and electrical attachments. 

Ones. What kind of current is used for 
operating electric elevators? 

Ans. Either alternating or direct current. 



244 



AUDELS ANSWERS ON 



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PRACTICAL ENGINEERING 245 

Ques. How is the transmission of current to 
the motor of an electric elevator controlled ? 

Ans. By an electromagnet controller operated 
through a switch in the car. 

Ones. What sets and what releases the brake 
on an electromagnet control elevator? 

Ans. A spring or weight sets the brake, and a 
solenoid releases it. 

Ques. How may considerable power be wasted 
in operating electric elevators ? 

Ans. By careless handling, that is, making un- 
necessary stops and starts. 

Ques. What are limit stops? 

Ans. The safety devices used to automatically stop 
the car at the upper or lower limit of its travel. 

Ques. What limit stops are usually placed on 
the shipper rope? 

Ans. Buttons or knobs against which the car strikes, 
causing the belt to be shifted, or power cut off. Such 
buttons or knobs are not sufficient protection in them- 
selves, as they are apt to slip or break. 

Ques. What is the most common form of 
motor limit stop ? 

Ans. A gear wheel working loosely on an extension 
of the drum shaft. Should the car overrun its limit, 



246 AUDELS ANSWERS ON 

either on the up or down trip, jaws on the hub of the 
loose gear engage with jaws fastened to the threaded 
shaft, causing the loose wheel to rotate. This sets 
in operation the gear which turns the shipper sheave, 
thereby reversing the motion of the elevator. 

Ones. Describe briefly the mechanism of a 
hydraulic elevator. 

Ans. It consists of a cylinder and piston with one 
or more rods connected to a crosshead which carries 
the sheaves over which run the lifting cables from 
which the car is suspended. 

Ones. What moves the piston? 

Ans. Water under pressure admitted by means of 
suitable valves causes the piston to move from one 
end of the cylinder to the other, and back again. 

Ones. How is this motion transmitted to the 
elevator car? 

Ans. By means of the sheaves mounted on the 
crosshead which carry the lifting cables. 

Ones. In what position is the cylinder placed ? 

Ans. Either vertical alongside the hatchway, or 
horizontal in the basement of the building. 

Ones. How are the valves of a hydraulic ele- 
vator operated ? 

Ans. In some cases by a hand rope passing through 
the car and over small sheaves at the top and bottom 



PRACTICAL ENGINEERING 247 

of the hatchway, and connected with the main valve 
in the basement. By pulling this rope down the valve 
is opened, and the car will ascend, while pulling the 
rope up will cause the car to descend. 

Ques. What safety devices are attached to 
this type of elevator? 

Ans. Two balls are attached to the hand rope, one 
near the bottom, and the other near the top. These 
balls come in contact with the top, or bottom of the 
car, according as it is going up or coming down, and 
being carried along they, of course, move the cable, 
thus actuating the valve, bringing the car to a stop. 

Ques. Mention another safety device con- 
nected with hydraulic elevators. 

Ans. Safety clamps under the control of a speed 
limit centrifugal governor which causes the clamps to 
grip the guides and thus hold the car. 

Ques. How is this safety governor operated? 

Ans. By means of a small cable connected with 
the car and moving with it, which passes over the 
sheave pulley of the governor. 

Ones. Why are some elevator pistons fitted 
with two piston rods ? 

Ans. To prevent the piston, and crosshead from 
turning or twisting, and also to strengthen the con- 
struction. 



248 



AUDELS ANSWERS ON 




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PRACTICAL ENGINEERING 249 

Ques. What other methods are used for 
manipulating the water valve, besides the one 
already described? 

Ans. Running ropes, and standing ropes, either of 
which may be operated by means of a lever, or wheel 
in the car. 

Ques. Do these devices directly operate the 
main valve ? 

Ans. No. They operate a small valve called the 
piston valve. 

Ones. What is the function of the pilot valve ? 

Ans. When opened it admits water under pressure 
to a small cylinder with piston connected to the main 
valve stem. This actuates the main valve, which in 
turn, by its movement, closes the pilot valve. 

Ones. Upon what does the amount of opening 
given the pilot valve, and consequently the main 
valve, depend? 

Ans. Upon the distance the lever in the car is 
moved from the central position. 

Ques. What is meant by central position of 
lever? 

Ans. That position in which there is no flow of 
water either into or out of the cylinder. 



250 



AUDELS ANSWERS ON 



Ones. What is the result of moving the lever 
too quickly to central position when the car is 
moving at a high rate of speed ? 

Ans. The motion of the car will be arrested with 
a sudden jerk. 




^^i^ii|i«^ 



Fig, 118. — Pushing type of horizontal hydraulic elevator. 



PRACTICAL ENGINEERING 251 

Ques. How many kinds of horizontal hy- 
draulic elevator are in use? 

Ans. Two. One is the pushing, and the other the 
pulling type. 

Ques. Describe the action of the pushing 
type. 

Ans. The car being at the bottom, the pressure of 
water is admitted behind the piston which then moves, 
pushing the crosshead and cable sheave and lifting the 
car. 

Ques. Describe the action of the pulling type. 

Ans. It is the opposite of that just described. 

Ques. Is there much difference in the valve 
mechanism of the horizontal, and vertical, types 
of hydraulic elevator? 

Ans. Very little except a few minor details. 
Ques. How should an elevator rope be fast- 
ened to the drum? 

Ans. It should be made long enough to encircle 
the drum at least twice when the elevator is in its 
lowest position. 

Ques. What water pressures are used 
generally for operating hydraulic elevators ? 

Ans. From 150 to 200 lbs. per square inch. In high 
office buildings where high speed service is required 
greater pressures are used. 



AUDELS ANSWERS ON 




Fig. 114. — Standard plunger elevator. The 
car is fastened direct to the plunger, and 
in small unbalanced elevators this fast- 
ening may be only just enough to hold 
car to plunger, but for balanced ele- 
vators the fastening between car and 
plunger must be strong and reliable, for 
should car part from plunger the counter 
weights would jerk car up against over- 
head work, with the chances in favor of a very serious accident. Plunger 
elevators are never overbalanced as the power acts only in one direction, the 
up stroke of plunger. Enough weight of car and plunger must be left un- 
balanced to cause the car to make the descent at the proper speed, when 
empty. As the plunger goes up the pressure under plunger diminishes by an 
amount corresponding to the height of water that displaces plunger. This 
is where the variable counterbalance is applied to the plunger elevator. To 
equalize this change of pressure the rope or chain that supports the counter 
weight must be of such size that the wieght per each foot of length passing 
over the overhead sheaves will be equal to half the weight of one foot in height 
of water displacing the plunger. The entire mechanism is shown in the illus- 
tration, from which the operation is easily understood. 



PRACTICAL ENGINEERING 253 



Ques. What is a plunger elevator? 

Ans. One in which the car is placed directly on 
top of a plunger or piston. 

Ques. Describe briefly the mechanism and 
operation of a plunger elevator. 

Ans. A cylinder is set vertically in the ground 
under the center of the car, and the length of it is 
slightly greater than the travel of the car. In this 
cylinder is a plunger whieh carries the car. Water 
under pressure is forced into the cylinder which lifts 
the car, and allowed to run out at the top when the 
car descends. The cylinder is always full of water. 

Ques. What is the usual diameter of the 
plunger? 

Ans. 6H to 7 inches. 

Ques. How is it constructed? 

Ans. Of lengths of polished pipe, joined together 
with an internal sleeve, and having its lower end closed. 

Ques. What pressure is ordinarily used on 
this type of elevator? 

Ans. 150 to 200 lbs. per square inch. 

Ques. How is the top of the cylinder ar- 
ranged ? 

Ans. With a packing gland through which the 
plunger moves up and down. 



254 AUDEL ANSWERS ON 

Ones. What is the purpose of a pilot valve? 

Ans. To give better control of the main controll- 
ing valve. 

Ques. Why can not a plunger elevator be 
overbalanced ? 

Ans. Because the power acts only during the up 
stroke of the elevator. 



W^F^/ <0^^- ^^ ^r^ -^jr^- -^^j- 4^^/ .<^r >•. -iy<f>-". ^r^ w&t 



'Knowledge is power, and the price of knowledge ^| 

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BOOK S fi 

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■ EDUCATIONAL PUBLISHERS |*| 

J ' : "\ 63 FIFTH AVE. .-. .-. NEW YORK 



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Written so they can be easily under- 
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with reliable and helpful information for 
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These books are self-educators, and " he 
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HAWKINS' MECHANIC AL DICTIONARY 

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3 



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Index. 

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f Mb f/M 

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PRICE, $4, DELIVERED 




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THIS treatise is 
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— LATEST : CONCISE : PRACTICAL — 

' I "HE object of this book is to give, in the easiest 
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Technical 



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IT It gives the latest improvements in established appli- 
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with the useful and valuable data presented regarding 
the manufacture of ice; and the preservation of food 
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If The 250 illustrations and descriptive diagrams (of 
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Horse Powers, How to Figure for 
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Index and Useful Definitions. 



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A list of subjects, which are fully 
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Introduction; The Steam Engine; 
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house, and many others. 

The book also treats generously 
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Engir 



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15 



STEAM ENGINE INDICATOR $* 



THE work is designed for the use of erecting and operating 
engineers, superintendents, and students of steam engineer- 
ing, relating , as it does, to the economical use of steam. 



The following is a gen- 
eral outline of the subjects 
defined, illustrated and pre- 
sented most helpfully in 
the book. 

Preparing the Indicator 
for use; Reducing Mo- 
tions ; Piping up Indicator ; 
Taking Indicator Cards ; 
The Diagram ; Figuring 
Steam consumption by the 
diagram ; Revolution Coun- 
ters; Examples of Di- 
agrams; Description of 
Indicators; Measuring Di- 
agram by Ordinates ; Plani- 
meters; Pantagraphs, Ta- 
bles, etc. 



He who studies this 
work thoughtfully will reap 
great benefit and will find that there 
is nothing difficult or mysterious about the 
use of the Steam Engine Indicator. This knowl. 
edge is necessary to every well-informed engineer and will 
undoubtedly be highly appreciated and a stepping-stone toward 
promotion and better things. 




The work is fully illustrated, handsomely bound, and is in 
every way a high grade publication. 



PRICE, $1.00 



THEO. AUDEL & CO.. 



63 FIFTH AVENUE, NEW YORK 
16 



HAWKINS ' ENGINEERS 
LIBRARY 



EVERY Engineer, Superintendent, Machinist, Electrician or 
Power User should have the well known " Hawkins' 
Works *' for study and ready reference. The seven books 
shown in illustration are the most complete and helpful works 
published for the practical man, convenient in size and well 
bound, containing 2.268 pages, 5,171 ready references on en- 
gineering practice, l f 188 questions and answers, 444 standard 
rules, 1.258 illustrations and diagrams, making them a mine of 
the best and most reliable information obtainable. Sold on 
very easy payments as shown below, 

$1.00 MONTHLY, 




ORDER 
TO-DAY 



SPECIAL EXAMINATION PRIVILEGE 

Upon receipt of following blank, properly filled out, 
the complete Library of 7 Volmnes will be 
sent you, express prepaid. If upon examination you 
find them satisfactory. Si.oo is to be sent to cover 
your first payment, and then $i.oo each month until 
the books are paid for, $12.00 in all. 



MECHANICAL DRAWING $2 



THE work has been carefully arranged according to the 
fundamental principles of the art of drawing, each theme 
being cleady illustrated. A list of the subjects are given 
below: 



Chalk Work ; Preliminary Terms 
and Definitions ; Freehand 
Drawing; Geomet- ^ 

rical Drawing ; ^a&S?* 



— Drawing ; 
Drawing 




Mate- 
rials and In- 
struments; Mechan- 
ical Drawing; Penciling; 
Projection; " Inking in " Draw- 
ings ; Lettering Drawings ; Dimensioning 
Drawings; Shading Drawings. 

Section Lining and Colors ; Reproducing Drawings ; Draw- 
ing Office Rules ; Gearing ; Designing Gears ; Working Draw- 
ings; Reading Working Drawings; Patent Office Rules for 
Drawings; Useful Hints and Points ; Linear Perspective ; Useful 
Tables ; Personal, by the Editor. 

The book contains 320 pages and 300 illustrations, consist- 
ing largely of diagrams and suggestive drawings for practice. It 
is bound in dark green cloth with full gold edges and titles ; it is 
printed on fine paper, size 7x10 inches; it weighs 33 oz., and 
will fit into any engineer's or mechanic's library to good advan- 

tage. ' PRICE, $2, Postpaid 

THEO. AUDEL & CO., 63 FIFTH AVENUE, NEW YORK 

IO 



ELECTRICITY FOR ENGINEERS $2 



THE introduction of electrical machinery in almost every 
power plant has created a great demand for competent 
engineers and others having a knowledge of electricity 
and capable of operating or supervising the running of elec- 
trical machinery. To such persons this pocket-book will be 
found a great benefactor, since it contains just the information 
that is required, explained in a pratical manner. 

Plan of Study 

The following is a par- 
tial list of the topics dis- 
cussed and illustrated : 

Conductors and Non- 
conductors : Symbols, 
abbreviations and defini- 
tions relating to electric- 
ity • The Motor ; The Care 
and Management of the 
Dynamo and Motor. 

Electric lighting ; Wir- 
ing; The rules and re- 
quirements of the Na- 
tional Board of Under- 
writers in full ; Electrical 
Measurements. 

The Electric Railway; 
I/ine Work : Instruction 
and Cautions for linemen 
and the Dynamo Room ; 
Storage Batteries; Care 
and Management of the 
Street-Car Motor ; Electro 
Plating. 

The Telephone and 
Telegraph ; The Electric 
Elevator ; Accidents and 
Emergencies, etc., etc. 

One-third of the whole book has been 
devoted to the explanation and illustrations 
of the dynamo, and particular directions relat- 
ing to its care and management ;— all directions 
being given in the simplest and kindly way to assist rather 
than confuse the learner. 




It contains 550 pages with 300 illustrations of electrical ap- 
pliances ; it is bound in heavy red leather, (size 4%x6J£ for the 
Socket), with full gold edges and is a most attractive hand- 
ook for Electricians and Engineers. 

PRICE, $2, Postpaid 



TMEO. AUOEL & CO. 



63 FIFTH AVENUE, NEW YORK 



ENGINEERS' EXAMINATIONS $2 



TIS work is an important aid to engineers of all grades, 
and is undoubtedly the most helpful ever issued relat- 
ing to a safe and sure preparation for examination. It 
presents in a condensed form the most approved practice in the 
care and management of Steam Boilers, Engines, Pumps, 
Electrical and Refrigerating Machines, also a few plain rules 

of arithmetic with examples 
of how to work the prob- 
lems relating to the safety 
valve, strength of boilers 
and horse power of the 
Steam Engine and Steam 
Boiler. 

It contains various rules, 
regulations and laws of 
large cities for the examina- 
tion of boilers and the 
licensing of engineers. It 
contains the laws and reg- 
ulations of the United States 
for the examination and 
grading of all marine en- 
gineers. 

The book gives the under- 
lying principles of steam 
engineering in plain lan- 
guage, with very many sam- 
ple questions and answers likely 
be asked by the examiner. 

It also gives a short chapter on the " Key 
to Success" in obtaining knowledge necessary 
for advancement in engineering. 




This helpful volume contains 200 pages of valuable informa- 
tion not elsewhere obtainable ; it is bound in rich red leather 
with full gold edges and titles : it measures 5x7}^ inches and 
weighs twenty-two ounces. 

PRICE, $2, Postpaid 



THEO. AUOEL 4 CO., 



63 FIFTH AVENUE, NEW YORK 
12 



STEAM BOILER PRACTICE $2 



THIS book of instruction on 
boiler-room practice will be 
of great help to firemen, en- 
gineers and all others who 
wish to learn about this important 
branch of Sleam Engineering. 

It treats on materials, coals, wood, 
coke, and oil and gas, fuels, etc., their 
composition, properties, combustive 
value, also on combustion and evap- 
oration. 

Giving the practical rules to be 
observed in firing with various fuels, 
management of steam boilers, pre- 
vention of foaming , tools and fire 
irons ; covering stationary, marine 
and locomotive boilers. 

It enumerates sixty important 
points of cautions to be observed in 
the proper management of boilers. 

It contains a description of and full 
treatise on stationary, marine and 
locomotive boilers, and the historical 
development of boilers ; specifications 
for boilers ; riveting ; bracing ; rules 
for finding pressure or strain on 
bolts. 

. It gives inspectors rules relating to 
braces in steam boilers. Also rules 
and tables for calculating areas and 
steam and water space of boilers. 
_ It treats on boiler tubes, construc- 
tion and drawing of boiler sections ; 
defects and necessary repairs ; inspec- 
tion of steam boilers; mechanical 
stokers' corrosion and scale, boiler 
compounds, feed water heaters, 
.injectors, pumps, boiler settings; 
pipes and piping ; steam heating, 
chemistry of the furnace ; boiler 
making ; plumbing, and hundreds of 
other useful subjects. 

It states several plain rules for the 
calculation of safety valve problems 
and those sanctioned by the U. S. 
inspectors. 

The volume has 330 pages and 185 illustrations and di- 
agrams. It is 6 x 8}4 in. in size and weighs 28 ounces. The 
binding is uniform with that of the "Calculations" and "Cat- 
echism of the Steam Engine," being bound in heavy green cloth, 
with ornamental titles and edges in gold. 



-0 !9£ 



PRICE, $2, Postpaid 



THEO. AUDEL & CO., 63 FIFTH AVENUE, NEW YORK 
L 13 







LIBRARY OF CONGRESS 

minium 

029 787 254 








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